Overall, I'd say the 920 is of much better value. It comes packaged with a few other impressive upgrades: a bluetooth remote, extra suction mounting plate (for sticking on the dash as opposed to the windshield), and a live traffic readiness (the 920T version comes with live traffic info out of the box, but it doesn't work in Canada and also isn't sold here either). The remote, however, is the best thing going for the 920. Instead of having look at the GPS, a driver can just press a button on the remote to have the voice prompt repeat directions, change a song, or even meddle with the menu (though none of these are recommended during driving).
Correction (4/19/08): Forgot to add that the Tom Tom 920 comes pre-loaded with North American and Europe maps. Also, since we exchanged the 720 for this higher-up model, the price has dropped to $399.99--that's $50 back to us (and $150 drop from the original price of $549.99). Imagine Futureshop's initial profit margins!
Below are a bunch of pictures I took of the unboxing process:
Tom Tom Go 920 still in its plastic wrap
All the contents of the package
The build quality of the remote is especially high--feels fit for almost any modern car's interior