I'm using a 7290 on Rogers, and am very happy with it as a phone and e-mail device... I use a Jabra BT200, and I agree with the comments from others abou the volume being a bit too low for use in some noisier environments, although sometimes that has a lot to do with the person on the other end as well...
Realistically, I don't think that the 7100 has all that much over the 7290 in terms of technical specs
as a phone (ie, things like RF signal quality, audio quality, etc). It has a few more phone-like features, such as user-replacable ringers and so forth, but from a purely technical quality point of view, I think the two devices are pretty on par with each other.
I think the real reason that people tend to get a 7100 if they're looking "primarily for a phone" is that the form-factor and keypad is much more like a cell phone, and is therefore attractive to people who primarily want a phone.
As someone else who uses both
functions heavily, I would suggest a 7290 as the better choice, simply for the full-size keyboard if nothing else (I've tried the 7100's SureType, and although I'm sure I could get used to it, I wouldn't even think of trading in my full qwerty thumb keyboard for it).