I finished the campaign last night. When you beat the game you unlock Marcus and Dom from Gears of War and the ability to use your custom character in the campaign instead of the default people. It took maybe 8 hours or so (that's including the time I spent playing with Cravis too though). It's definitely a game that's better than the low reviews it received. I tried a multiplayer match but didn't like it because it was just free-for-all so I'll have to get into a team game sometime tonight. I got all the way up to level 33 with one faction and 29 with another faction just from playing as them in the campaign. 
You can choose to only do team elimination matches if you want to. This is one of the few games where I also like team-based matches where everyone starts with sniper rifles...played in a four-on-four match and was able to sneak up on the other team and take them all out with a VS they weren't using that was right near where they were all camping.

I don't like that ranked only offers three games types. Player matches have more, but most people seem to be only doing ranked. Love the "Cube" multiplayer stage. It's a small-sized map inside an arena, with an audience cheering for you and an announcer making some light commentary.

That's pretty cool that you can level up from the campaign, too. Certainly explains all those high-level players I've been seeing!
How do you get Wesker? Is he a pre-order bonus from somewhere?