I plan to use it for WiFi tethering.
Used is cool. I'll consider Android, iOS and Windows Mobile. I'll try to avoid Symbian and Blackberry OS but I might consider if it hits the correct price spot. No J2ME devices please.
Android preferred. I'm comfortable with rooting and so Android 2.2 is not a must.
And, yes, WiFi is a must too. Display quality and other stuff don't matter.
I found some myTouch 3G on eBay but that's about it. Whatever happened to all those old budget smartphones?