I've never owned an iPhone, but I have seen the progression from the iPhone 1G, to the iPhone 2G which added 3G data support, the iPhone 3G, and now the iPhone 3GS. When it first came out, not many people heard of it. Now the iPhone 3G is one of the most popular phones in the USA. Why so popular? Besides the fact that the iPhone is Apple-made, Apple-easy to use and convenient, it's been tested through trial and error: namely, the iPhone 1G and 2G. Much like the iPhone, the iPad will have several issues before it reaches a level of "this-is-good-enough-for-the-average-user" like the iPhone 3G. (If you remember, the iPhone 1G didn't even have copy and paste functionality.)
The question of the day (and I've had several people ask me this): should I buy an iPad? If so, should I get 3G or no 3G? If no 3G, how many GB of space should I get? If I get 3G, should I get 250 MB of data ($15/month) or unlimited data ($30/month)? Is there a contract on the iPad's data service like there is on the iPhone? Can I use my iPad as a phone? What *is* the iPad? I'll try to answer all these questions in the following.
First, what is the iPad? Well, it's essentially a "glorified iPod touch" as many have put it. It lacks calling functionality, so no, it cannot place and receive phone calls by default. Now, with a VoIP program like Skype or some other calling service, that functionality will be possible–assuming you have Skype credit or place calls only to other Skype members! The iPad features (to my personal disappointment) the iPhone OS, a version that allows you to change the background of your home screen unlike previous versions. The iPad also is able to download ebooks with the "iBook" app, as well as create documents with Pages, spreadsheets with Numbers and presentations with Keynote–all Mac OS X apps ported to the iPhone OS. I personally would have liked to see the Mac OS on the iPad, as the iPad is similar to a tablet computer–which currently most tablet computers run computer operating systems like Windows XP or Linux (although a few are running Android and hybrid mobile OSs). Another thing lacking on both the iPad or iPod is a camera. In fact, on the iPad, one would almost expect a forward facing camera for video calls and the like. The iPad still lacks multitasking, and has no way of expanding the 64 GB max of storage space, no USB ports, no SD card slots.
You can see the price differences between Wifi only and Wifi + 3G models. However, the big question is are those AT&T data services 2-year contracts like the iPhone? The answer (thankfully) is no, as of right now. It's $15 a month for 250 MB of data (about a quarter of a GB) or $30 for unlimited data–once again, no contract so you can stop the data services anytime you want. The ability to use 3G also sends the price up quite a bit. I had a friend ask me if 250 MB is enough–initially I thought not, however if you are using the iPad like you would an iPhone to surf the web, 250 MB would probably be enough (using things like Skype would use a lot of data). Assuming you don't use your iPad's internet all day long, you should be fine.