Several months ago, shortly after I’d bought an ebook reader, someone asked for advice on them, and I sent my thoughts. Since then I’ve reposted that email a few times. Next time, I’ll just send this link.
The short version: I have a Sony and love it, mostly. Great battery life, and I can take notes, but the screen is dim and I can’t print the notes. I also read on my iPod Touch, but right now I don’t have a way to put books I’ve bought from the Sony store onto the iPod.
The long version:
I was buying an ebook reader right around the time of the buy button fiasco, so I didn’t do much research into the Kindle. Also, I thought it’s keyboard was a feature I don’t need, so I’d already pretty much ruled it out.
I’ve been very happy reading books on my iPod Touch, so had been looking forward to the iPad and its larger screen, but the Nook/Kindle/Sony have longer battery lives. Obviously, depending where you’re reading, that may not matter, but I like not having to recharge my book every day, and I wanted something to take on a 12+ hour one-way, two week trip.
I tried the Nook at our local B&N, and ended up getting a Sony Touch (their mid-range reader).
Some comments on the Sony vs the others:
* Many people like the e-ink screens better than LCD; I find it a bit too dim, and of course you can’t read in the dark. All three readers have that problem.
* The Nook’s color strip at the bottom means you get less screen per device area, which seemed silly to me. Kindle has the same problem with the keyboard. The Sony Touch has a nicely sized edge and narrow buttons; it’s pretty much all screen.
* On the Sony (except for the higher-end one) you can’t buy wirelessly, so you have to wait to buy books until you’re at the computer (horrors!). (Aside: My favorite comment on articles about the Nook coming out was “This is the 21st century, I shouldn’t have to walk to the bookstore to download a book.”) Their store and  software are easy to use, although somewhere along the line I had to get some Adobe login, which was a pain. It’s easy to organize and sync files and to find them on the device. I found navigating the Nook more difficult, though obviously I didn’t try it for as long.  Alas, the Sony store is full of DRM, but the reader’s happy to handle books from every other store I’ve found as well.
* I’ve had no trouble putting all sorts of free content (mostly PDFs given away by publishers) onto the Sony. It also reads every other format I’ve run across. Except Kindle, but I haven’t yet found something I needed that was only available on Kindle.
* The Sony Touch doesn’t seem to do a sans-serif font. The Nook and Kindle both do, as far as I can tell. All three can make text ridiculously gigantic. Although I prefer sans-serif on a screen, it’s easy enough to read the serif font. The quick look I had at iBooks looks awesome; much prettier than any of the three readers.
* Annotations: The Sony has a stylus with which I can mark up text (including my own RTF files), and I can see the annotations on the computer.  I think the Nook and/or Kindle only let you annotate certain types of files, but don’t take my memory’s word for it. Anyone know about the iPad? Unfortunately, while I can make annotations on my Sony and sync them back to my computer, *I can’t print them*.  I marked up some manuscripts for critique on a trip, and I had to copy all my scribbles onto paper. The other option was to take screenshots on my computer and print them. (I used the stylus to make notes. You can also type notes, and maybe those can be printed?  Also, you can highlight words, and you can get a list of all the words you highlighted. I didn’t find that particularly useful for critting…) I’ve run across a python script that would fix this, but haven’t tried it yet. The annotations are stored as image files on the computer, so I assume the lack of printing is a deliberate anti-piracy decision rather than a technology issue. Still, it makes it useless for anything but marking up my own manuscripts.
* All three have the e-ink page turn flash, which the LCD screens don’t. It’s not annoying; most of the time I don’t notice it.
* Supposedly you can borrow books from the library with the Sony, maybe also the other readers. I haven’t tried it, and our local library doesn’t have a very big ebook selection.
* Battery life and charging: My Sony wouldn’t recharge from an AC socket on our trip. (My husband has an AC USB adapter that works great for the iPhone/iPod, so I don’t know if the limitation is something Apple put in or an issue with the Sony.) Sony sells an AC adapter separately. Â That said, I read more than a book and a half on the way over, made annotations on about 150 pages, got a low battery warning, and read another book plus a bit on the way back – the battery never quit on me. Â I suspect all three readers have about the same battery life, Â though.
So, after several months of using the Sony, what do I think? If I were buying based on battery life and/or price (which I did), I’d get the Sony. Anything else, the iPad.