I'm currently using the Xperia X10 which uses the Android OS. Had it about a month and could smell a faint burning smell and found it's a not too uncommon occurrence for the motherboard to 'blow up'. Virgin mobile replaced it within 2 days and fingers cross this one lasts more than a month.
I've had the Iphone 2G since the day it was released in the USA. And im planning on upgrading to the Iphone 4 soon.
Got an HTC Hero a few months ago, bit old but I bought it cash rather than on contract so it was all I could afford. Sucks how I don't get FroYo, but so far I'm liking it. It does have some annoying tendencies like insisting I've got new messages even though I've already read them...