Last month I was one of the first to buy an iPad; and now I have had three days with a new iPad 3G and can share some first impressions.
First thing I can confirm from my own experience is that battery life is in line with Apple's projections. When I use 3G I notice a reduction in battery life of about 10 percent.
Other than this, and the obvious advantage of having constant Internet via the new AT&T micro-SIM, it is very much business as usual.
The bookreading experience is identical and I have found my productivity increasing as I get used to the iPad way of doing things.
I have taken to Pages and like it very much. I've had no difficulty printing to my HP printer. Photographs also print easily using HP's iPrint app.
I've also become more familiar with the virtual keyboard after a month of practice. In a previous post I said I wouldn't want to type any long documents. Now I'm not so sure, and connecting a keyboard lays all remaining reservations aside. Just remember to pack that Bluetooth keyboard if you intend to write a novel.
The service from AT&T here in Washington DC is much as I have come to expect from the iPhone. However, the iPad is generally so much faster in loading pages that the 3G service, in comparison, feels incredibly slow. I understand that this is not any fault of AT&T but more the fault of the iPad for being so fast. I have had no problems streaming video from sites that don't insist on Flash Player and I am very happy that the iPad can do all I need.
In general use I continue to be addicted to my iPad and it is quite clear that the overall impression is very much the same whether you go for the 3G or the cheaper wifi-only models.
Reading books the iPad way continues to be a delight. Even on my sunny deck I can read without problems. The iBookStore is a bit skimpy on titles at the moment but, of course, there is also the Amazon Kindle store. I just love how seamlessly and painlessly Whispersync gets new purchases onto the iPad. And, of course, the same system keeps all my books in sync across iPhone, iPad and Mac (and, of course, on the increasingly irrelevant Kindle if I had one). To my delight, iBooks imports anything in the ePub file format, so I can even get my cult Perry Rhodan Schundroman from a site in Germany.
So there you have it. The choice between the wifi and 3G models is clearcut and very straightforward. The basic wifi models offer everything except 3G. They can be used with personal wifi router such as the MiFi, so you are not giving up 3G for ever if you choose the cheaper model. On the other hand, the small premium of $130 for 3G inclines me to conclude it is the better buy. At least you are keeping your options open and it could be an easier beast to sell later on eBay.