Buying books from the Kindle Store is addictively easy. I shudder to think how many books I'm going to buy over the next year. I've bought a couple dozen ebooks over the past month, mostly cheaper paperbacks. I've also downloaded a ton of free ebooks from Mobileread and other sites, and made a few ebooks using the Mobipocket Creator and content from Project Gutenberg (they're not really ready for primetime, with no working ToC, or I'd upload them to MobileRead).
Although I've bought a few technical books on the Kindle, I really think I'm leaning towards the physical copy when the ebook is the same price... and we're talking north of $25. This would change if I could get a bigger ereader (something like one of the new Fujitsus shown at CES) where it would make sense to read a technical book.
I'd also like to get an AZW reader for my PC that would be 'keyed' to my Kindle (perhaps tying my Kindle serial # to my Windows license), so I could read my Kindle books on a PC. Shouldn't be a big deal for Amazon to eventually do this, and if the license allows one to share ebooks on up to six Kindles, then this could easily be extended to up to six ereaders regardless of platform.