In today's USA Today there is a review of the color HipTop (known as the T-Mobile Sidekick). They love the color screen but don't like the phone features. However, since T-Mobile is offering unlimited data plans, most users will probably focus on Internet activities anyway. According to the review, it's AIM feature is great.
"The presence of color normally drains power. Danger bolstered the battery, though it's still nothing to get jazzed about: about 60 hours of standby and 31/2 hours of talk. The new device also carries 32 MB of memory, double that of its predecessor. The increase translates into about 2,000 contacts and 50 notes, vs. 1,000 and 20 before, probably adequate for most of the users T-Mobile has in mind. But heavy-duty business types with greater requirements are out of luck because the unit contains no slots for adding external memory."