I have two netbooks, a 9" tablet classmate purchased from work, and an original Asus Eee PC 7" with 4GB Ram and the celeron processor (before the current generation of Atom and only runs at about 633 MHz). I haven't used the classmate much as I just got it.
But, I love my Eee! I just came back from a business trip and the Eee was a great traveling companion, light and easy to carry. I have a 5-hour battery to use when traveling. It has wonderful connectivity, plays movies, and I find the form factor convenient for reading txt and HTML books. I turn it to portrait-mode, make the display full-screen, turn the backlight down as low as possible, and hold it like a book. It's so comfortable that sometimes my hand automatically starts to try to turn the page! For evening reading in bed it is perfect - no extra lighting needed and quite silent.
That being said, I think the 10" is probably the best general netbook size as it is easier to browse the WWW and read PDF business documents. Some come with a 9-10 hour battery and most have a hard disk option. Asus has announced a 10" Eee tablet for the end of the year (if I remember correctly). That might be interesting if there is a page-turn button on the frame.
Cons:
Netbooks are not pocket-portable the way that the current ereader devices are and nowhere near the battery life. Even with the backlight turned down, the LCD is probably harsher on the eyes than eink (but I am not certain as I can go 2-3 hours with my 50's eyes in comfort which is fine for my needs). It seems that the classmate tablet display is not as comfortable as the Eee - don't know why, perhaps the tablet layer makes it brighter? I can't seem to lower the brightness as much even at the lowest setting.
Pros:
Netbooks are fully-functional PCs, with Internet access, dictionaries, video playing, and run programs including office applications such as a word processor and spreadsheet. Don't have to care about book formats and re-formating PDF to fit a tiny screen. Book page turns are instantaneous and without the flashing effect.
I am rambling a bit, but I've given it some thought since I'm in the opposite position from you: with 2 netbooks and a mp3 player with audiobooks for my purse, do I also need a dedicated reader device? I decided to go ahead and give it a try and am now waiting for my jetbook to arrive. So, my two-cents-worth is to get the netbook AND keep one of your Kindles for when you need the portability.
P.S. - I found out a side-benefit of a netbook-as-book-reader: no one can tell that you're reading a novel during a boring business meeting!
