Just finished this. It was fine. The gameplay of the series didn't translate super well to the less linear structure of most of the levels, and the introduction of super simplified crafting neutered the very interesting and well implemented barter system and economy of ammo from the previous two games.
It's also still about as buggy as 2033 and Last Light, and that buggyness is exacerbated by the more open levels.
All that whinging aside, the main strengths of the series -character, story, and atmosphere- is some of the best it's ever been. I particularly loved the in-between missions parts on the train where you can just hang out with all the characters and listen to super long conversations, share a cigarette, play the guitar or just lay-down and rest with your wife. It's all very well put together and effectively presented and it really got me emotionally invested even if a lot of the gameplay sections got kind of plodding.
It remains a very handsome series (when it's not bugging out) and the environments still have some of the best use of detail I've ever seen, both in terms of graphical fidelity and set dressing. Few game studios are better at making every little piece of every map feel authentic and alive and lived in.
While I really really like the organic character interactions and care than went into the many simple peaceful scenes between bloodbaths, I don't think the actual plot of the game is nearly as coherent or well structured as the first two games, due in no small part to the much broader scope. It's more of a theme-park ride between a bunch of different regions and factions (likely from the book) than an effective narrative with a satisfying arc and it just kind of ends abruptly the minute it runs out of ideas.
I feel kind of bad complaining so much about a game that so much care went into and still elicits very real and genuine emotional investment in a way that very few games do (just sitting on a bed with Anna just holding her hand while she talks was peaceful and heartwarming in a truly profound way), but I've been trying to be less forgiving of meaningful flaws in games that I like, especially if they're from a series that I like and am biased towards.
If I'd give Metro 2033 a 3.5/5, and Last Light an 4/5, I think i have to give this one a 3/5. Some of the stuff that's been good from the beginning is probably the best it's ever been, but the stuff that was bad is still bad and even more of an impedance than ever. The changes to gameplay and overall structure were unneeded and don't really add anything and even take some things away that were unique and effective in the previous games. I'm glad I played it, but I'd replay the first two again before I replay this one which works out because half of the reason I'd want to play any of them again is just to spend more time with the characters and atmosphere.