Im still working my way through it. Im on Act 4 right now. My cousin finished it today, so I kinda know how far I have to go. But, its still been a crazy and fun ride so far. He said the ending was great too, so Im pumped.
The one thing that annoyed me is that if you have multiple people playing it on the same PS3 and each person is on a different Act, it has to install every time you load it cuz it has to change acts. That is a bit annoying. But I get over it as soon as I start playing.