I'm on 5-3 now, initial verdict:
This game is a fun rental but i don't think i'll be buying it, if i had bought it like i intended to i'd probably end up selling it. I do like it overall though, it's probably my second favorite game this year after Portal 2.
Why i'm not buying it:
Act 4: While not terrible, i never want to play it again, ever.
No new game + or anything outside of the main game, which isn't horrible, but since i don't want to replay all of the main game that really goes against it. I imagine a lot had to do with keeping the budget down, but a Mercenaries type mode with this game could be a lot of fun too, it has a lot more mechanics than RE 4/5.
While i really like the world, it could use more "characters", while the game overall has a ton of personality it certainly lacks enough memorable people, most of the time you're killing a different assortment of enemy types and there aren't many allies/enemies that stand out.
Definitely recommend everyone play this game if they are still on the fence though.