[EDIT]: Looks like someone's made a petition based on this post. Seems like a good idea to me - it's the kind of thing that B&N may well see the benefits of!
For the actual act of reading, the nook works well - certainly a good start for any ereader. The hardware is solid, the screen is pleasant (although the pixels are a tad noticeable; one holds a book much closer than a laptop or TV) and the page turning buttons have a satisfying click. A less noticeable screen refresh would be nice, but then e-ink is still fairly new tech. The colour touchscreen should have rounded it out perfectly, making complex navigation a breeze.
The issue is the software. It's not even a matter of big, complex problems, it's just a few minor but blindingly obvious omissions. The real shame here is that all of the major failings could be put right with a few lines of code; B&N could have it done within a week. Hell, it's the kind of thing the open source community would have straightened out in an afternoon.
All in all I'm still happy with what I got for my money, although I'd say $150 is slightly on the high side of reasonable. It's a special purpose device, after all, so 98% of its use is simply flicking through pages. The rest of the time, though, is spent using ancillary functions that are just barely adequate.
The lack of any search or jump options in the library is going to be a problem for any collection of non-trivial size. It lists ten books per page, without so much an option to skip to a letter of the alphabet, search, or even skip to a given page. On a device that can hold many thousands of books, manually clicking through one frame at a time will very rapidly get to be a serious problem.
The screensaver's issue is simple: you can't turn it off. Although e-ink apparently needs to be refreshed periodically to avoid images 'sticking', there's no reason for the device to wipe your page and replace it with a pretty picture. It just means that it takes a few seconds every time to get back into your book - not the end of the world, but a little jarring. Why not just leave the text up, ready to pick up and read, much the same as paper? Have the device blank the display and refresh every few hours if it's necessary.
Although some might not consider it core functionality, the audio player is a major enough selling point to be worthy of comment. In short: who decided to design an MP3 player without playlists? Even just allowing selection by folder structure would be fine. It's so basic that it should go without saying, but as it stands there's not even the ability to separate audiobooks from music. There's also the dead-battery waiting to happen due to the rather strange fact that sleeping the device doesn't pause the music.
To add insult to injury, not only did B&N take the time to add a general purpose web browser to the 1.3 firmware (which is all but unusable on an e-ink screen) while a simple go-to-page function within the books wasn't added until 1.4, they also released a 1.4.1 hardware revision which makes the previously available jailbreak unusable. It's an Android device, they don't sell apps, and the standard software is quite happy with epub files from any source - the idea of preventing root access seems to me to be completely inexplicable, even from the most cynical 'big business' perspective. The upshot is that one can't even circumvent the problems by installing a couple of simple apps - say a specially designed library manager and MP3 player set up to work with the dual screens.
So there you go. A nice device with an overall decent interface, marred by some very obvious missing features. I'd still tentatively recommend it, especially in light of the Kindle's poor format support, but it's a real shame that the potential for an excellent touchscreen interface is going completely untapped.