I have a Skil IXO2 and love it. It is small, super light and comfortable to use. It only has forward and reverse at 200 rpm's, but the Lithium-Ion battery lasts forever. It charges quickly too when you do need to charge it. The only thing it doesn't have is an adjustable clutch. But the power isn't all that much and the slow speed allows you to stop it when the screw gets 95% torqued down. I then finish it off with my Hudy hex drivers.
Hitachi makes a Lithium Ion cordless driver that used to be $80 but is now been reduced to $50 at Lowe's. It comes with two batteries, charger, has two speeds and most importantly an adjustable clutch. Everyone I know that has it says it is the BOMB. I have one waiting for me under the Xmas tree
As for bits, I have the 2.0mm and 2.5mm Mugen hex driver bits. They are very high quality but aren't cheap.