I for one like the TouchWiz look, but hey everyone has their own tastes and I think thats a strong point of Android that one is able to change this. Here are some apps I think you should get or at least try out
Google Sky Map - cus is cool
Listen - great way to get podcasts, I use it to keep up with CarTalk(comes out on npr, very funny show)
Shazam - hear a song on the radio and want to know what it is, use this
ShopSavvy - Find a product, scan its barcode to lookup prices, and make lists. I use it to keep track of books I find in the store I may want later.
But everyone's needs/wants are different so I'd say browse the Market and see what catches your eye.
Oh and unless you are a true geek able to walk that dark path, I'd say stay away from root-ing/flashing/etc. No faster way to screw things up and leave you with an expensive brick you cant take back to Tmo. Too many times have I seen someone cry out on the forums saying they need help. If you cant understand the instructions and note the warnings, stay away.
And have a happy day.