I've played a bit of 5th Ed.
Overall I'd say it manages to plough a reasonable path between the perhaps excessive crunch of 3rd Ed and the more simple style of 1st & 2nd Ed, without the alarming incongruities that the early editions suffered from.
First, there's a lot less to play with than in 3rd Ed. Much simpler character build, and from my experience so far a less steep power climb up the levels. They've retained the concept of more flexibility in spell-casting they introduced in 4th Ed. but have done away with that edition's video game style to a large extent. Characters begin being quite capable, but not already superheroes.
I've not seen any class dominate the game so far, but my experience is limited. They seem to have gone to some effort to balance the classes, and have nerfed some more spells along the way. Thet haven't managed to recapture the early editions' incredible versatility in the abstract utility of spells, but the more flexible casting rules allow more versatility than you got in 3rd Ed.
Feats are an optional thing, to replace ability increases instead of in addition to them. That means a lot less scope to build yourself a monster, which was where 3rd Ed really shone if you had the experience to learn all the best combos.
In short, there's a lot about it I like. There's a fair bit about it I'm less sold on. It seems to work pretty well, but I do wish they'd drop the overreliance on grid positions (why can't I stand on the lines?). It's the one aspect where the abstract nature of the rules really grates against the fantasy feel of the game.
"...with frikin' lasers!"