HTC Widget I use:
People: Allows you to make a 3x3 grid of favs. You can dial them from the widget. Makes it easier then scrolling through the address book.
Clocks: all of the HTC clocks are sweet. Some people may not see this as a selling point, but a lot of people are buying widgets/apps to mimic the HTC ones.
Google voice search: I use Google a ton, and having it with my original Hero I loved it, missed it with my Moment & am very glad it is back now that I have a Hero again.
Setting widgets: BT, Wi-Fi, GPS, ect. These all come stock with HTC and they work great. You can DL some from the market, but I have not found any that work as smooth.
For the fat fingers, get Better Keyboard. If takes the little space left over and turns it into a much better keyboard. I was skeptical, but it really makes a huge difference.