The enemies in Sin aren't too exciting, although they are pretty challenging to fight. Most are humans, though there are more mutants and cyborgs deeper into the game. It would have been more exciting if more mutants appeared earlier to break up the monotony of your human opponents. The weapons don't seem too weak in multiplay, and the body specific damage system doesn't imbalance deathmatch. The Ultimate Sin So far, Sin sounds like a pretty good game with a few stumbles in weapons and monsters.
Some levels even load twice.
I tried playing the game without the patch, but couldn't get through it - the load times were just too long. Activision did produce a patch that fixes these and other bugs, but the load times still felt long even when reloading the same level. Even after the patch, I noticed some serious bugs. In one subway level, the mutant boss failed to break a hole through a wall, leaving me trapped in the level with no way to progress to the next stage. In the Water Works Part 2 level, the boss monsters, Eon and Peon, never showed up.