The HD is a nice phone, and runs really smooth. But if you text a lot, I'd recommend the Z, just because of the keyboard. It's just way nicer to type on then on the on screen keyboard.
The android market works really smooth. You've got a lot of free apps (66% free) and all of them work great. On the HTC are already a couple of news and weather apps. You can download angry birds for free, as well as most of the Ping apps (if you want to ping) Most of the games you can download are all lite versions, but will keep you entertained as well.
If you've got any other questions PM me