Well I finished Gun and all in all it was a really fun game. It reminded me alot of Red Dead Revolver but this is a ton better. The gameplay is fun. It's not frustrating like most games. The freeroam aspect of the game is very fun and you don't feel as contained as in most games.
The side missions are fun, most of the time, and once you beat the game its even better. You get to make your guy a freakin juggernaut finishing up all the side missions and such.
When I first saw this game I thought it was going to be stupid and exactly like RDR but it holds it own. Fast paced, and tons of crap to do, not to mention get some of the coolest dismemberments.