I own a kindle 3g keyboard and recently purchased a Nook Simple Touch as a present. I can't really say anything about the kobo, and everything I have to say about the Kindle touch is based on the previews I've seen and a few articles.
The nook is light (but not as light as the kobo), well-balanced, fast, responsive, and has excellent form factor. The sides of the nook have a softer, more rubbery feel than the kindle, which feels hard, although probably not as hard as a metal device. The nook is also thicker (perfect thickness in my opinion) with a concave back, making it easier and more comfortable to hold (in my opinion) than the other perfectly flat readers. To me the kindle is a bit too thin, and after holding the nook str, feels a bit less balanced.
The nook does have a browser and wifi internet, but the browser is very buggy. It can be rooted, however, which allows you to install android apps, including the kindle app. The nook does not have audio, but it does have microsd storage.
The kindle's advantages are its ecosystem. Notes and highlights are backed up in a plain text file called myclippings, which can be exported. They are also backed up at kindle.amazon.com. You can also store up to 5 gbs worth of personal documents to the cloud. The kindle does not have any external storage.
I don't think Amazon will remove the 3g wireless capabilities of the keyboard version, especially since the install base of that version will only decline in time. I highly doubt Amazon, which is one of the most intelligently run companies on the planet, will remove a feature that a device had before, although it could happen considering that the browser is listed under "experimental" features. Web browsing on an ereader, however, is a chore. I would not base my purchasing primarily on this feature.
As far as navigation, the kindle is imho probably the best you can get with keyboard navigation, but it isn't as seamless as touch. Still, the keyboard works very well, and it allows you to do everything you need or want to do with relative ease.
There really doesn't seem to be any substantial differences between the touch and keyboard readers, other than that the touch versions will probably be slightly faster (they are supposed to have an 800 mhz processor, compared to a 532 mhz processor for the keyboard version), and have a feature called x-ray, which just seems like a file that comes with certain books with the wikipedia entries for certain characters, events, themes, and ideas in a book. But unless you have well over a thousand books on your device, the k3 is still fairly speedy and responsive. The notetaking, highlighting, browsing, and shopping experiences all seem to be essentially the same.
I've had the kindle keyboard for over a year, and it is a terrific device. I don't know if you'll like the keyboard or not though, so if you are considering buying this device, I'd suggest going to a Target or a Best Buy to try out one of the kindles on display.
Last edited by spellbanisher; 10-23-2011 at 05:14 PM.