I finished the campaign in one sitting some years ago and I don't remember anything good about it to be honest. Multiplayer was fun and fresh though, played it for years.
If only Valve fixed the anti-cheat system and actually explained how ranking system works it could've been a lot better. Also it had it's hitboxes broken for years, we don't forget about that.
apart from bugs and average shooting mechanics, i can say this is one of the best western rpgs that ever came out. i had so much fun replaying it over and over, just exploring the world and trying many different things each time.