I have both an iPad and a Nook (Barnes and Nobles' 'Kindle') and was quite enthusiastic about them at first, and now use them only rarely. I've gone back almost exclusively to printed books. And I read a lot.
For me, electronic books are mostly good for reference works, such as travel guides. I also suspect they'd be good for authors who write technical books that need to be frequently updated, as with people who write photography or computer or software guides. If, for example, you wrote a guide for Lightroom 3, you could update it with each new revision, and keep your book absolutely current, where it might otherwise become obsolete. This would be especially useful in small technical niches where not huge numbers of books are sold.
They would be very useful for people who have limited access to good book stores.
The Kindle is somewhat crippled because it isn't yet offered in color, as far as I know. The Nook is, which means that it can reproduce color photographs, which is especially useful with guide books.
Unfortunately, none of the electronic books have put much emphasis on such things. Instead, they emphasize best-selling novels, which I find are more comfortably read in paper. Also, I find it much easier to browse books in bookstores -- there are a lot of visual cues to book quality that you don't see on an electronic book, and I want to browse extensively before I buy a novel. When I do find a book, I then go ahead and buy it on the spot, rather than noting it and buying it later on the Nook or iPad.
I find the greatest use for the iPad is in travel, with the cell-phone hookup for internet browsing. I have been driving across the American southwest, through small towns, have had my girlfriend use the iPad to check Starbucks locations, and had her take me directly to the proper exit, and then straight to the Starbucks. You can also look at maps, attractions, etc., as you travel. I do a lot of travel, and keep the iPad in the car.
I should note that the Nook has a common hack (Google "nook hack") that turns it into a fully functional Android tablet, just like a smart phone...the equivalent of an iPad.
Ctein, the well-known photo printer and photographer and free-lance genius, also recommends the iPad as a photo cache and review platform. I think it would be excellent for that, although I use a MacBook Air.
JC
