A device that only works on the 700mhz band will be useless to anyone that travels internationally. It needs to support other means of communicating if it is to have any success in the business world.

If it supports Boingo's wireless client, then it could quasi get away with only the 700mhz support plus WiFi support. There are a few metro WiFi networks in Europe that Boingo would provide automatic roaming to. But limiting it to WiFi would still mean there would be a lot of areas you'd have no coverage. So ultimately, it also needs to have some form of wireless data coverage (ideally via HSDPA with fallback to GPRS).

I'd also add that for me, personally, it'd have to do Skype if I was to ever even think about purchasing one.