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i've used the 3G while driving. i don't have a GPS in my car, so i used the Maps app to navigate. also Yelp and FindNearMe

i've used the 3G with Starwalk as well
 
I have an iPhone 3GS and an iPad 3G.

I got the 3G model not for the data connection but for the GPS. I use navigation apps both in my car and while flying a small plane (I have a private pilot license). I like location-based apps too.

For car navigation the iPhone is actually enough. I like the visibility of the iPad screen but the iPhone is more convenient to mount in a rental car and to keep at a convenient viewing angle. For the plane, though, there are far more detailed maps with things like radio frequencies and airport names that are much easier to read on the iPad.

I did activate the data plan to try it out, and have not wanted to turn it off since then. I like being connected at all times. I could JB my phone, but I haven't wanted to deal with shorter battery life and other issues I've read about when you JB. I also typically prefer the newest OS features over just about any JB app. That is why I am at the latest firmware level and I don't think there was a JB available until recently. However, there are new OS versions also coming out soon.

If I do decide to JB, it would be only for using MyWi or TetherMe (I haven't looked closely enough to know which one I'd want). For now, one device can back up the other if one battery dies, and I have not concerned myself with the ethical implications of violating terms of service. I can even use my iPhone headset to make VoIP calls from the iPad (mainly using Skype).

I would not want a MiFi kind of device because I don't want to carry and charge yet another device. My iPad, iPhone and laptop are already too much to carry around during frequent business trips.
 
I have an iphone 4 with unlimited and and ipad with unlimited.

I keep both unlimited plans. I don't want to jailbreak my phone, at least not for now and I don't want to be switching sims and take the chance of AT&T finding out and terminating me. I use a heck of a lot of data on both, over 5GB streaming netflix and pandora, mostly at work.

The fact that we will never see an unlimited plan on the ipad is another reason I keep my ipad unlimited plan.
 
The beauty of the 3G is still that it's an on-and-off option. You may never need to activate it but when you do it's there. And GPS is a nice feature as well, especially in a strange city - not merely for GPS use but for GPS-enabled apps that help you find restaurants or other points of interest (as well as the augmented reality apps that may be viable if there's a rear camera). The 3G is all about potential.

I did a 2-week road trip through about 6 European countries last summer and the 3G iPad was the best travel companion ever.

Extremely good point. No way in hell am I gonna want to sit around in the hotel bar with these guys after riding together for hours lol. Ughh, I really hope all models have 3G and I don't have to pay extra for it, because I think I've been convinced.
 
I never use 3G on my iPad because I keep it at home. However when I travel it is extremely useful to have the iPad because it isn't looked to a carrier. This is not the case with the iPhone, besides in many places it is very easy to set up a data plan from the iPad (not on the iPhone though). I have actually used the iPad for directions and stuff when traveling abroad. :D
 
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