The whole screen is on springs, so a light touch can act like a cursor (copy & paste?) while a harder press acts as a click.
Yes, RIM has an App Store starting up.
Verizon devices rarely have WiFi, simply because their 3G is so widespread. (Personally, I usually use WiFi for private Slingbox at home.)
The Storm supports tethering.
I'm thinking seriously of getting one for my wife, since she needs Verizon up here in the hills. The iPhone is a poor option around here.
Whether its UI is as "compelling" isn't the main factor. What matters most is that it's on Verizon... and the iPhone isn't.