I asked myself the same w=question before I upgraded. Even hesitated for a week or two. But the fact of the matter is that the speed difference is the biggest factor. Clicking links/meus/messages/etc are isntantaneous as compared with the 7290. maintaining larger mailboxes, numerous calendar entries, etc slows your 7290 down but the 8700 keeps chugging. Message truncation seems to be less of an issue on the 8700 as compared with the 7290.
The difference is more than having the newest toy. I can never go back.
Why have a pentium 4 when a pentium 2 does the trick? That's what the difference feels like.
Blackberry Curve (8300r) on Rogers (Toronto, ON) with hosted BES. Previously: 8700r and 7290.