Android phones, apps and tablets

have any of you fandroid lot got a new phone on upgrade and sold it straight away?
is it worth doing? i have no idea what models are worth getting/selling?
i have my own iphone4 so can either get a sim only deal or as T-mobile have fucked me off by turning of my voicemail (and giving me a free month because of their incompetence) i think they will offer me a good deal on something.

failing that it's moving to 3 but i hear plenty of horror stories about non existent customer services.
T-mobile for all their faults have a decent 3g service that's much better than orange so O2 are the only other option.

I didn't sell my brand new one in the end (opted for the slight upgrade of Desire -> Desire HD).

1. Have a look on the t-mobile site (or call them up) and see what sort of deals you can get for an upgrade of various new phones.
   
2. Check eBay and see how much each of the various phones in selling for.
   
3. Get the one with the best deal that still offers you a good return for your money.
   
   

All obvious advice that you've probably already thought about. If you can upgrade now and can afford £35ish a month, get the latest and greatest (Sensation or Galaxy II?) and flog it.