I have a 7100T and I love it. You get used to typing on it and as long as you don't have to write long emails, then it does a great job. I have been known to write fairly lengthy emails on mine without too much of a hassle. I really like the 7100 - so much so that I bought a 7130 from verizon that should be arriving this week!
The 8700 looks cool, but its too frikkin big. It feels like you're putting a brick to your head when you talk on it.