I have a Hanlin Clone (BeBook one), Pocketbook 360, and a kindle 2. I have used Sonys and Jetbooks enough to form an opinion.
My go-to reader these days is the 5in PB360 because of its size, ergonomics and software flexibility. The Kindle 3 is getting pretty close to the Pocketbook firmware in flexibility. Both the PB360 and Kindle are very stable.
To be honest, *today* the first question a would-be 6in reader buyer needs to answer is why *not* Kindle WiFi? They have the best screen, the best embedded store, and the lowest price.
If you really value a touchscreen interface and ePub file support then Sony or the larger Pocketbooks make some sense.
If you value customizability and having things *your* way, then you'd want to look at the Pocketbook line. And at 5in the PB360 is really sweet and fun to own.
But the first thing you need to decide is *where* you're going to get your DRM'ed ebooks; Amazon or somewhere else. 'Cause the market today is split right down the middle: Amazon vs everybody else. Once you settle that, the choices get easier to make.
Things may change next week, but this week...

Good luck!