My new Nook arrived yesterday. It's my first eReader.
I have to say that I'm a little disappointed with several aspects of the thing.
Let's start with the design of the hardware; I wonder who's bright idea it was to sink the screen below the bezel and then make the walls of that screen well glossy. The former causes a slight but annoyingly distracting shadow on the side of the screen when you have a side light source and the latter causes reflections when you move the Nook to a more direct light source, for instance when you are trying to stop the shadows from a side light! Yes, you can, with effort, position the Nook in such a way as you get neither but seriously, why should that be necessary?
I must admit, I could live with the shadows but the glossy reflections are, to use a bit of colloquial, doing my head in. And it has got to the point where I'm considering taking a brillo pad to them.
I won't say much about the "buttons". Ha! Bendy plastic more like it. But they are far too stiff if you ask me.
I must admit that after the first 3 hours it did stop freezing, crashing and rebooting although I did stop playing with it too much in an attempt to keep it running. I did open it up and reseat the battery which may have helped too I guess.
It's heavier than I expected too. It shouldn't be I know as I saw the specs, but when it's in your hand, combined with the form factor, that weight translates to, "heavier than I'd like". Add the Oberon cover and it feels almost like an iPad.
Onto the navigation. I won't say much, but the word "disjointed" comes to mind. Whoever thought a touch screen like this on an eReader was a good idea should be fired. To me the colour touch screen seems like a marketing gimmick that adds very little to what could be done with buttons and in a lot of ways it's intrusive (glare anyone?). I feel sorry for the poor developers stuck with this hardware and having to come up with some sort of usable interface - they failed miserably of course.
I really wanted to like the Nook and had high expectations. I thought I'd done enough research of eReaders when I narrowed my choice down to the Kindle and Nook but obviously I didn't. Although I didn't like the idea of a touch screen, I thought I could live with it as I got ePub support which the Kindle doesn't have (forgetting Calibre et al ePub -> Mobi conversion here for a moment).
But now the Kindle 3 has been announced and I'm very glad that I have it on pre-order. Yes, no ePub but I'm willing to convert everything if it doesn't mean silly touch screens, shadows, reflections and glare.
I know a lot of people like the Nook and although I can't really understand why, I accept that preference is a very personal thing. What I will say is this; if you are in the process of choosing an eReader I would suggest that you try to see one and hold it in your hand before you buy and, if like me you can't, then consider your available options very carefully before you buy. Personally, I will try damn hard to get used to the Nook before I go back to my iPhone reading but I'm guessing that once the Kindle has arrived, the Nook will be put in a cupboard somewhere, never to be seen again.
A couple of positives before I finish; the eInk screen in direct daylight is awesome. I'm amazed how good this is and it really does blow away any other medium I've seen for reading in bright light. It's seems a little yellow and dim in subdued lighting though but I guess that's why they invented reading lamps.

The other good thing; the Oberon cover is simply incredible. Amazing workmanship and worth the $75 without a doubt. It's a little heavy though, so if you're looking for a light cover you need to look elsewhere.
Oh, and I guess there will be Nook fanboys that will say I'm unfairly bashing the love of their life. Well, think what you will, but this is my unbiased opinion and I've no particular interest in other tech one way or the other; I just want the best product that suits my needs.
I hope this post will be useful to someone.
Edit; Take a look on page 3
here for a photo comparison of the K3 and Nook.