Most people will recommend what they use and there's nothing wrong with that because what they use might suit your needs very well. Now for me I have a Sony PRS-505 which I love but I have been tempted to pre-order the new Kindle 3 for these reasons
1/ Pearl screen
2/ WiFi (not bothered about 3G but that's an option if you think its something you need)
3/ Kindle Store ease of getting books
Now if someone ask me what to buy I would just say (and i'm from UK so as said above our options are not as good as in USA) go for a Kindle 3 at £109 for the WiFi version or if for some reason you don't like the Kindle maybe the Sony PRS-300 = £99 at Waterstones (if you don't mind the 5" screen)
Anyway im sure all the readers have good and bad points these are just the 2 I really like out of them all and I would not spent silly money on an e-reader so things like the Kindle DX are way over priced (unfortunately).
So Good luck in finding your perfect e-reader
Kindle 3 here
Sony PRS-300 here