I read a ton of programming books for fun (mixed with business and fiction), and spend a ton of money on amazon buying paper books, so I was naturally interested in the Kindle DX as it would save me a lot of money and space in my apartment.
Anyways, I've had mine for about 2 months now, and haven't regretted it at all. Every programming book I've purchased reads just fine, and I have had no issues what-so-ever. The only thing that kinda bugs me is that some books (I'm looking at you, pragmatic bookshelf) don't have a kindle version, however, most do.
Also, if you turn your 3G off, the kindle will run for well over a month without a recharge. I've had mine on for the past 1.25 months or so without charging, and that thing still has 25% battery left. Crazy.