I'm definitely getting an iPad, but I've been trying to think how useful 3G will be if I already have an iPhone?
Almost every time I connect to the Internet today I have Wifi access. If I'm out of WiFi range with my iPad, I'll still have the connectivity via iPhone if I ever need it. The real question is whether the iPad will have must-have exclusive apps that require 3G?
I'd be astounded if Apple and AT&T would allow iPad tethering to an iPhone.
GPS is another thing. According to the technical specs, only the 3G iPad has it. GPS would be nice to have if maps were downloaded to the device prior to getting outside Wifi range. I'm surprised there is no GPS chip in the iPad. Maybe we'll get surprised at the launch? And if so, would the added cost for the 3G iPad be worth it if only it had a GPS chip in it? The augmented reality apps could be awesome.
I think I'd like to grab the Wifi model now as an early adopter and then replace it with a generation 2 device when it comes out in a year. I could save the $130 price difference plus the (optional) 3G fee now. Heh, but will I kick myself in August once the app developers get their hands on the thing?