I like the idea that they're releasing a SDK for it. But there's a big limitation of all Kindle's currently on the market, and that's the slow refresh speed of the screen. If you have one, flipping pages in a book is fine, but browsing a page on the web seems awfully slow (could be due to an un-optimized browser).

I'm not sure what full-screen frame rate it supports, but my hunch is in the 2-3 FPS range or less (someone please correct me if I'm wrong - I'm guessing). AFAIK there's not even a Doom port to hacked Kindle's yet, which is usually a badge of honor saying "this device can play games and has some power to it".

Any apps developed for it would likely be staticly-displayed on screen. Board games would work well, email clients, IM clients, to name a few. Amazon would have to release a new model with a better screen to, say, address what Apple appears to be doing with their upcoming tablet, and allow for applications which require refresh rates which can display motion.