Well the Rock Band kit doesn't come with a bass/2nd guitar so you need to buy a second one to get a whole band BUT the guitars don't come out until April and GH3 guitars don't work with Rock Band thanks to the whole EA/Activision bitchfest so basically it'll be a few months before you can rock out with a whole band. The drums aren't actually all that big and they can be put on a table if you connect the drum pads directly to the base instead of using the leg pieces, it saves some room.
Rock Band guitar section is much tamer than GH3, and a lot of songs are downright boring as all hell, same with some songs for drums and for vocals. That, for me, is the problem with Rock Band. Most songs in GH are made to be hard to play and be diverse and a lot of fun to play. Rock Band has to compromise to make songs that will be more fun as a band but sadly aftr you have played "Say it ain't so" for the 46th time in World Tour Mode (since you play the same songs over and over and over at different gigs) the game starts to grind me.
Also, you can't progress past a certain number of fans, which unlocks new venues, unless you crank up the difficultly. So, basically you need to be able to play on hard/expert and have at least one friend who can play at the same level with you. For me, that also breaks the game since people I play with won't lay higher than medium so I'm stuck at 260,000 fans and will likely never get past it.
That said, Rock Band is still a lot of fun with a group and some better DLC will help keep it fresh.
