Also there's a low-end Android phone by HTC called HTC Tattoo. But I would say no to it since you get what you pay for. Not many apps run on it coz of the type of screen it has.

Also no to Sony's Xperia X10 coz it runs Android 1.6 although it's a new phone.

HTC Desire is awesome. Also it has the same specs as Nexus One minus the Google logo. It also addresses some N1 problems :)

I would suggest that you investigate if the manufacturer is the kind that would support you by offering OS updates if a later version of Android releases. HTC seems to be one. I dunno abt Motorola.

Get something that runs the snapdragon processor coz there's a very high possibility that these phones will get updates to a new OS version coz it's capable of running them better.

A tip - develop using the emulator first and then buy a phone :)

P.S: I'm getting a Desire later this month when it releases in my country.