Really, really, really take the sanitation seriously. We've had several people post here saying "Mr. Beer sucks! I'm getting into some REAL homebrewing!" then after some questioning, it turns out they didn't sanitize well and the beer was infected. Mr. Beer isn't the greatest, granted, but you will make some decent beer and learn a lot if you sanitize well, switch LME or UME for the booster, and follow the directions.
Good luck!
Monk
P.S. Oh yeah, and leave it in the fermenter for at least 10 days, maybe two weeks. Trust me. It's worth it. If your beer isn't done fermenting when you bottle (due to cold temperatures, slow yeast, etc.) it will be "bad news for the brews".