I've been a heavy O'Reilly Safari user for a few years now, so I had already made the transition to digital versions of technical books. I also never made notes inside my books (I keep notes in separate files), so I didn't miss this ability when I transitioned.
I have a kindle 3 for reading e-books. Before that, I had a Cybook Opus. Both of these devices are not suitable for reading pdf's. While they can technically render them, the screen is too small to display content formatted for full page widths, and there is nothing out there that can reformat pdf's with acceptable quality. If your goal is to read pdf's, only large-size screens like the kindle dx or ipad will be suitable.
When reading books formatted specifically for the kindle, I find that the reading experience is pleasant enough that I forget it is not paper. The kindle 3 is the first e-reader I've seen where the e-ink screen is on the level of quality of a printed book. I have the leather cover, which folds open like a hardcover book, and the combination is very pleasant to hold (very book-like feeling). The device is light enough and thin enough to not have the clumsiness that some books can have. I also love the fact that it always remembers the page you were on. Paper books can be really annoying that way.
For technical books, I exclusively use safari, so I was very pleased when they launched a kindle 3-compatible version of their mobile site.
Good points about mobile safari books:
- Pages load fast and are pleasant to read.
- Content is reformatted for the screen.
- The page turn keys make it convenient to scroll down the page.
- Making bookmarks inside of safari is straightforward, and bookmarks are shared with the regular web version (you can also make notes, but I never do).
- Awkward navigation between book sections (have to pick out a small link with the D-button)
- Awkward navigation in general (when you're navigating around the web site, you really notice the lack of a touch screen)
- Sometimes wifi connectivity is lost for a minute or two, where other devices remain connected. I got the wifi-only version. This is probably one of these "it's just you" problems.
- Scrolling down the page can leave a little ghosting (due to how the e-ink screen works). I'm not really bothered by this as it is very subtle, but that may not apply to everyone.
Bottom-line for the kindle I can say that it's a very good book reader, even for technical books, but only if the books are formatted specifically for the device, and only as a passive experience. As an interactive device (beyond page flips), it's weak, mostly due to the lack of a touch screen. Whether you like it or not heavily depends on the source of your books, and of the level of interactivity expected.