Being a nerd, I'm more and more appreciating the hackability of the desire. I now have a new operating system (android 2.2) with full (i.e. not mobile) flash support, and lots of nice little tweaks. And because the OS is open source, and hacking is semi-supported (HTC turn a blind eye to it, and even purportedly leak early test versions of code to hackers), there is a much bigger community of people modifying and messing around with it.
Like the battery meter at the top, now, rather than being just a bar, on my phone it is a little bar with a percentage number written on it, saying what percentage of battery is left, which is really useful when you're having a big day of phone, gps, web etc. use and need to know accurately how close you are to needing a charge.
I've even got a hacked pre-release radio update, which improves the signal, meaning I get 3g in my house now, which I don't think any other phone has ever got, you used to have to go about 200m up or down the road before you got it.
The magic of this is that because it is so hackable, doing these hacks is relatively user friendly – once you install a hack, there are even auto-updaters for the hacked versions, so you can get over the air updates, like you would for a normal unhacked phone. Magic.
Joe