Thane Krios -RIP *Bullet to the face*

I guess sending him as the stealth guy was a bad idea because it was an obvious choice. But i don't feel to bad if its only him, he was sick anyway so he dies a heroic death. in a random cut screen sort of way.

Interesting. The amount of randomization in the final encounter seems to play into more replayability.
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TAZ

I chose to create a distraction and used Legion to run the ducts. I never let the heat get too high.

When it came time to deal with the bugs, I picked the option to push through the room (not "They must have a weakness.") and used Jack to do it.

I had Grunt escort the doctor back to the ship.

Every team member survived their missions. I was also very anal about getting all of the upgrades I could possibly get before doing the mission. No idea if that helped them survive or not.

Hearing that other combinations don't work, I may be a bit hesitant to experiment on my second play-through, since that's the one I'll be loading into ME3.

Here's all the information I got from my own playthrough and from the BioWare forums:

Spacebattle:
Each missing upgrade will result in a team member dying. If you take this teammember with you during the oculus fight, someone else dies.
-No Solaris Armor. Oculus beam slices through the bottom of the Normandy: Jack dies (don't know who's the alternative death).
-No Cyclonic Shielding. Engine core overloads: Tali (or Jacob) dies.
-No Thanix Cannon. Normandy goes Charge of the Light Brigade on us: Garrus (or Thane) dies.

Assault:
-If the Tech Specialist is not one of those listed below, they will die at the first rendevous.
-If the Heat Exchanger valves are not opened in time, the Tech Specialist will die and you have a game over
-If the first Fireteam Leader is not a leadership character, the Tech Specialist will die at the first rendevous.
-If the second Fireteam Leader is not a leadership character, they will die at the second rendevous.
-If the Biotic Specialist is not powerful enough, one of your current squad members will be swarmed by seekers and die.
-If the crew survivors are not escorted, they will die.

The following characters are the only ones that will succeed at their tasks:
-Tech Specialist: Tali & Legion
-Leadership: Miranda, Jacob & Garrus
- Biotic Specialist: Samara / Morinth & Jack
-Crew Escort: Anyone works

Not having a character's loyalty has different effects depending on what you do with them:
-Having disloyal characters in the above key roles will result in deaths, regardless of whether they are suitable or not.
-A disloyal crew escort will sacrifice their lives to protect the crew (the crew will still make it).
-Disloyal characters do not necessarily die if they are left to hold the line while Shepard fights the last boss.
-Keeping disloyal characters in your active squad prevents them from dying, except for...
-In the final boss fight, disloyal characters in your active squad will be crushed by rubble after the fight and die.
-If all team members are dead, Shepard misses the final jump and lets himself fall to his death rather than risk Joker's life (note that if you have all 11 teammembers, it doesn't apear to be possible to get them all - and thus yourself - killed).

-Normandy Crew:
If you do not go through the Omega-4 relay quickly enough after the Collectors kidnap the Normandy crew, the captured crew members will die off in the endgame. Who dies depends on how many missions you did after Joker plugs in the Overlord. Note that you can go anywhere you want in the galaxy, visit any shop, talk to anyone you want; only doing missions matters.

-If you use the relay immediately, everybody survives; Horizon colonist gets liquified instead.
-If you do one mission, Kelly, engineer Daniels, mess sergeant Gardner, and half the crew dies.
-If you do two missions or more, everyone except Dr. Chakwas dies.

The only random thing left for me is the part at the end where the remaining team must hold the line until Shepard kills the Contra throwback. It seems Mordin dies most often, but I've also seen posts from people for who Thane or Jacob kicked the bucket.
Character upgrades, loyalty and time taken to kill the boss doesn't seem to affect this. The current theory over on the BioWare forums is that either how well you dealt with people's loyalty quest or if you deliver a rousing speech has influence.

...
Yeah, maybe I'm overanalyzing this.

Analysis appreciated. Also, I didn't know that Morinth could join the crew. I'll have to give that a try on my renegade playthrough.
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TAZ

Wow. I didn't realize the decision tree was so complex. Yet on my first stab, I kept everyone alive.

In some cases, it was really intuitive. For example, I knew Legion was good with tech and far more likely to survive a wretched environment than Mordin. I knew Garrus would do a good job of leading a fire support team.

In some cases, it was completionist neurosis. You simply can't afford every purchased upgrade on your first play-through, but I did complete as much as possible, including all of the researched upgrades.

And, finally, in other cases it appears I just got some dumb luck.

I lost the crew of the Normandy, except the doctor. But I'm willing to accept that since I had no emotional attachment to anyone in the crew except Joker and the doctor.

The only kicker is now, you have to wonder: Will event X end up killing NPC Y when the Normandy II gets into a firefight in ME3 because I let those two people in engineering that really knew the ship die in ME2...

...You have a couple years to contemplate their loss.

I lost them the first time around, too. That was completely unacceptable to me (I liked Kelly, Rupert, and ESPECIALLY my new engineers), so on my second play through I spent an ABSURD amount of time researching stuff, scanning for resources, and upgrading my ship. I hit the Omega-4 relay loaded for bear and spoiling for a fight. I absolutely tore the collectors a new one, saved everybody, and blew up the station. I sent Tali into the ducts instead of Legion, but I don't think she even had a chance to really start sweating, because I was playing a Sentinel (took the AR when I got to pick an extra weapon proficiency and used my spiffy-neato collector AR from the preorder and picked slam as my extra ability) and tore through the opposition like a runaway buzzsaw. Between slam, tech armor, and the collector assault rifle, I scarcely had to stop my forward advancement at all, and Harbinger barely got to do his thing as I killed enemy platforms before they even got docked. If you played through and found the game a bit too challenging for your taste, try that combo next time. It was much easier than my Infiltrator.

I'm planning to play through ME1 and skip the romantic subplot so I can go for Tali, because despite the fact that she's an alien, that seems like the most genuine available romance out of the whole batch from both games so far. She's someone my character has known, trusted, and been trusted by for a long time. And having my extremely Paragon Shepard be the kind to go for a casual fling seems jarringly inconsistent.

The more times I play through this game, the more sorry I feel for the geth. Helpful tip, quarians: when your AI creations show their intelligence not by making a huge, coordinated attack (that they're MORE than capable of doing, considering they're all networked) but by asking you if they have a soul, you might want to at least consider that they may not be hostile...

So it is possible to get enough people loyal -- and enough research done -- yet still rush into the relay and save everyone? Hmmm. That would be nice. Conversely, I wonder how it will affect the next game to go in without loyalty missions done.

But now that I think about it, it doesn't matter. After the relay mission, it gives you the option to keep playing the game. So you could save everyone and still complete all of the loyalty missions thereafter.