New trailer reveals there will be 4 player co-op and new single player levels (and keyboard cat):

I agree that going through the original game with 4 players would be stupid, but it looks like they've designed completely new levels for the co-op that would make it work (a la Splosion Man). It could be interesting as long as they didn't half ass it.

I played this for a couple hours yesterday and it's pretty good. It's got the expanded levels from the SE, which is cool because I've only ever played the SNES version. The game looks and plays great and is just as fun as I remembered. There are 3 brand new single player levels you can unlock by collecting cans of worms in the main game. These are stand alone levels that you can play anytime via a menu option, they are not integrated into the main game.

The multiplayer levels are a bit half assed, but not awful. They're new levels which are based off the single player levels, but they feel kind of generic in comparison. Most of the quirky stuff that made the original game so fun are missing (ie. no cow launching, boss battles, andy astroids, hamster riding, bungee jumping, etc) so it ends up feeling a little tacked on.

Achievements range from easy to impossibly hard. I got half of them within an hour just playing the game normally, but there are others for beating the game in under 50 minutes and beating the game without dying that I'll probably never get. You can also unlock the Earthworm Jim suit for your avatar which is pretty sweet.