I have had it from April-2010 and am still using it. I got a Samsung Galaxy S for my wife (wanted her to have a better phone than I do !). To quite an extent, therefore, my analysis is likely to be a result of contrast than a pure take at HTC Desire.
I can say that I am becoming unhappy now. Single main reason being poor internal memory.
Unhappy with:
(1) Very poor internal memory: Extremely let down on this. In this day and age, to have 120 MB of space etc. seems like 2000/ 2001 type constraint. Even with Froyo, not everything can be moved to SD card. I have had to constantly battle out which Apps to uninstall and which to install again. Often, I keep swapping - a week of this and a week of another App and painfully part with some, never to use again. Despite Froyo update, I can't, hand on heart, admit to, especially to iPhone fanbois, that I can fill all my 7 screens with 16 Apps in each (four rows of Apps with 4 in each row). It's come to a point where I am even thinking of selling it on eBay and go for some generous model like Samsung Galaxy S. The surprising thing is even HTC Desire HD sports only 1.5 GB or similar ? Come on HTC, how much more is it going to cost providing a respectable 4 GB or 8 GB ?
(2) Sound quality: The speaker phone is very ordinary. Doesn't do any justice to the good Video playback display.
(3) Bluetooth being old version: Can't seamlessly connect to some devices since it's not the latest. I can connect with some basic bluetooth devices though.
(4) Native contact list (from HTC) isn't as rich as Samsung Galaxy S. But, that's just a minor gripe
(5) Copy + Paste not being as universal as you'd expect. It works within certain contexts, but I have often been let down when trying to do it across screens that mattered to me. Some of which could be Android's own limitations (as of now) but some others could be due to HTC Sense not foreseeing certain possibilities
(6) Screen washout in normal outdoor ambience: I am not even talking of summer sunshine when this would be practically useless without a torch ! Even in Autumn times, the screen display with maximum brightness on, is still dismal. Indoors though, it's second to none
(7) The inability to shut down HTC Sense without rooting (I don't wan to root it yet)