I have put a good 3-4 hours into it and here are my first impressions:
It looks really good (not as good as other games) but I can run it 1280x1024 at full settings (except AA which is 2x) and it never drops below 30fps.
The weapons, which I have only used about 4 or 5 are decent.
The open world is nice, but very tedious to drive for 30 minutes to get where you need to go.
The fire dynamics are pretty amazing! Drop a molotav cocktail and just watch the grass and trees catch on fire. Although they say that the fire reacts naturally, which it does except that it burns itself out at set time it seems. I had a huge brush fire going and it definitely had more places to go with the wind kicking up but it just died off. I guess the engine has it's limits.
AI: Not that good. I sat there in a 'camp' with 3 guys just staring at me. ANd they were definitely enemies.
The missions seem a little too repetetive so far. I felt like I was killing the same three guys through out the first 3 missions.
And I had the same issue as nstuff where I had to go to the bar but it wouldn't let me until I went to the arms dealer, which it didn't really tell me I had to do that.
One thing that I really like is the buddy system: There's one guy you meet near the beginning of the game that if you 'die', he comes and picks your ass up and carries you away from the action to heal yourself. THe whole time you pass out and wake up intermittently and see him blow some guys head off as he is carrying you. That's pretty neat.
All in all, it's a good game, just doesn't live up to the hype that everyone has been giving it.
Since some of us have it, I want to try and get a Hamachi game going. I really want to try the multi, but as I have a 'questionable' version of the game I can not with out the help of my friends! *hint hint*