Insane Mode isn't for the weak.
The online multiplayer matchmaking is somewhat better than the originals, where in the first game you'd have to host your own game or search for a ranked match. In Gears 2, they follow in Halo 3's footsteps where you can have your own party of friends(up to 5 depending on the game mode) and search for an opposing team. The problem with the matchmaking is that if you have 4 members and start the search you'll be looking for a lone member for a long time since with the NXE everyone now already has 5-man-teams.
The weapons have changed power-wise from the first game. The shotgun is still brutal in close combat, but it can't stop the all-powered: Lancer. In Gears 2 the creators thought it'd be fun to add chainsaw duels and give people a fighting chance to stop the chainsaw from cutting you in half... but what they didn't do is work out how to stop a chainsaw with any other guns, because you can shoot a opponent with any gun but end up getting chainsawed, it's a big problem for me.
The sound, graphics, and overall presentation is great and I haven't run into any bugs during single player or multiplayer. The game is awesome if you like 3rd person shooters and the story is real fun. Keep the kids away if you don't want to expose them to the violence and swearing that is rampant in the game.