I had one for about a month or two. The device worked as advertised and was a fine e-mail gadget. For me, it was overkill and that's pretty-much the sole valid* reason why I dumped it.
As a PDA and e-mail device, the 7100t was top-notch. Zero complaints. You do have to spend an extra $30 or so to get The Missing Sync, in order to sync with your Mac, but the program does work like it's supposed to. As a phone, the 7100t is only mediocre. I don't remember specifics, as it's been 4 or 5 months, but I remember profiles being a pain in the arse... Not nearly as flexible as on a phone only device. As just a phone, the BlackBerry is pretty big and heavy by today's standards, as well.
In summary, if I had the kind of job which required me to have 24/7 access to e-mail, then I'd happily accept another 7100t... That is until The Next Big Thing comes out. And hey, the best thing about the BlackBerry: It doesn't run Windows Mobile or Palm.
__________________
*I'm an admitted phone whore and have a new-in-the-box ROKR sitting on my kitchen island. It's going back. I waited breathlessly for the iTunes phone, but won't be activating it following bad review after bad review. I now have a (much more expensive) Sony Ericsson W800i on the way. That'll satiate me 'til the "real" iTunes phone... Like maybe one designed by Apple... Comes out.