I had this phone for almost two years and just replaced it with a Samsung Galaxy Ace. Overall I did like it and initially I was very impressed, however towards the end of the two years, I did notice it was becoming slower and less reliable which is why I decided to change. When two year contracts are standard, I feel a phone should be able to keep up!
Initially I loved the phone. The screen is one of the best things in my opinion. It's very bright and very clear, and also responsive as a touch screen. From pictures to text, I think the screen, particularly at the time I bought it, is such good quality. The glass is also very tough. I dropped my phone so much but it never cracked or broke, and only towards the end did it get scratched. Comparing this with the newer HTC Sensation (which my boyfriend has) and some other HTC models I've seen off friends, this is better on the Desire, as many of my friends screens have cracked.
The phone also has a nice build quality, and although some people find it a bit heavy, I liked this as it feels well built. That said, the case is easily scratched and this shows quite quickly. I also found that after about a year, where your hand holds the phone, the paint was coming off... literally just from holding the phone in my hand when texting. Not good!
The software is decent, and if you keep updated works well. Although after a while I noticed it became slower... I could have done a factory reset or something but I don't like to fuss with my phone too much and so this was a problem. I also found the internal memory was too small. I had a memory card in there and when I could I moved apps, pictures etc onto it but for some reason, the apps that were on the device's internal memory, such as facebook and messages took up so much room that I also had 'insufficient memory'.
Overall, I would recommend this phone because it is the first phone I've put up with for more than a year so it must be good, however, I wouldn't sign up for a two year contract with it again for the reasons above.