I liked it enough that I got 100% completion on the PS3 version at release and then just bought the complete pack a couple days ago for $6 to play through it again on PC with all the DLCs. I'm a sucker for anything related to that era though; I've read everything James Ellroy has written, L.A. Confidential is my favorite movie, I'm loving that new Mob City show on TNT, etc. ...so YMMV there.
It's far from a perfect game though, even to a huge fan of the genre. You play a character who is sort of an Ed Exley type, except considerably more of a douchebag at his worst. The plot has a 'wtf moment' about 2/3 of the way through in which he does something incredibly stupid. You have no control over either of those things, it's just how it plays out, and I found that irritating. Another complaint I had was that the city has an absurd amount of wasted space in it. If you take the time to collect all the movie reels after beating the game, you quickly realize that there's a ton of locations in the city that you never had any reason to go to. It's not a particularly short game but given all the troubles Team Bondi had while making it I had to wonder just how much got cut out in order to finally ship it.