Go T-Mo G1 (HTC Dream). It's a new platform, running Google's Android platform, but the open-sourceness is delicious. Compared to my friend's iPhone 3G, the G1 has a brighter (albeit smaller) screen, better contrast, some of the same apps that are available for iPhone (Shazaam runs faster on the G1 than on the iPhone in repeated tests) and some apps that the iPhone doesn't have (ShopSavvy, a nice price comparison app that searches the web and local stores around you after scanning a product's bar code... this app makes most iPhone users I've shown it to envious http://www.biggu.com/ )
Check out the G1!
Holy crap...old-timer Shen making a return for 2009?

Anyhow, I'm keeping tabs on the iPhone too. While the hardware and software is indeed spiffy despite Apple's "we know what you want better than you do" attitude, I don't think I can justify the cheapest data plan for it considering I have enough trouble paying $50 monthly for my current plan with Sprint.