Handcent SMS is the best texting app. Extremely customizable and very user friendly. I also recommend getting LauncherPro. It replaces the stock DX homescreens and is much faster than the stock launcher. It is also extremely customizable.
PowerAmp is a great music app, much better than the stock Android music player.
Pandora is also great for streaming music.
Telsa LED turns our LED flash into a flashlight, and can be placed on your homescreen as a widget for one touch on/off access, and it's instant.
Pulse News is a great news app and is highly customizable. I use it on both Android and iOS.
If you have any more questions or need help setting things up, send me a PM with your gtalk adress and I can help. I recommend trying to figure everything out first though because learning first hand is always great.
I love the smart keyboard and the fancy widget works better than the HTC weather widget......my home area wasn't working properly. I also like the smaller clock sizes on the fancy widget. Doesn't interfere with my hiding my homescreen . I do hope HTC can get their weather widget working correctly though.