I swear by my Dremel 8220 battery tool. It's the first battery powered one that I've been high on. Gobs of power, and no power cord to get in the way. I also have a Dremel 4000, but it doesn't come out often, the battery powered one is so good!
Once you get to use a good battery powered tool, you'll wonder how you ever used a corded one! I recommend a second battery, and there's even a spot in the case for the backup battery.