I thought I ought to mention this option for ebook readers ...
I just bought a
Viliv S5 mobile internet device. And yes, it makes a good ebook reader.
The Viliv S5 is a small tablet PC -- 5" screen, netbook-like specs (Atom 270 cpu clocked at 1.33GHz, 1Gb RAM, 60Gb hard disk, Windows XP, Wifi/bluetooth/USB), and weighs about 500 grams. Battery life is 6 hours in regular use, up to 8 hours with no wifi and the screen dimmed. The screen resolution is an eye-bleedingly sharp 1024x600 pixels. Build quality is very solid indeed, and it sells for around $599 right now (I bought a grey market import via eBay; Dynamism.com also sells them).
In the hand, it feels like a thicker (inch thick) version of the Nokia web tablets. The big difference is that it's a much beefier hardware spec, higher resolution screen, and a "real" operating system. (I don't like Windows, but while I've got a bootable Ubuntu partition, getting networking and touchscreen drivers up is taking some time. Ah well.)
FBReader and Calibre both run on the S5, and FBReader in 90-degree counterclockwise rotation works well. (It also runs Mobipocket Desktop 6.2.) I gather that eReader also runs happily. I've got Firefox on it as a web browser, and iTunes for music.
If you're used to using a big PDA such as an iPaq as an ebook reader, think of the Viliv S5 as being similar (albeit slightly chunkier) but running a full desktop OS and with a higher resolution screen. If your main thing is reading ebooks -- it costs about as much as an Iliad, and the battery life is slightly worse, but it's a far more flexible device as long as you're okay with an LED backlit colour screen.
And Viliv are launching a 7" model, the X70, very soon. (Don't confuse this with the S7, which is a laptop with a swiveling/tablet touchscreen.)