I got an iRex DR800SG yesterday (in your face iRex Europe, it costed 350€ instead of 500) and I used it for 1-2 hours with the original firmware and after that I installed the beta version. What I can say is that zooming in pdf make a HUGE difference and it's a big step forward. I'm glad I didn't get the reader before the beta version.
Here are my comments, probably some of them were said before:
1. Zooming is useful, but it can be made much better for landscape mode. A fit width to screen option is missing (this can be done manually, no biggie). And also it would be very nice to see the next part of a page when pressing the rocker, not the next page with the same zoom (I think you know what I mean, I can't express is better, or maybe I can: so if I see half of the page and I request the next page, I want to see the other half of the page, not the first half of the next page. Of course, in portrait mode when I zoom in just to skip the margins, I don't need this kind of browsing).
2. When displaying pictures, it would be nice to put a shortcut to browse to the next picture. Now, if I want to see the next picture I have to go to the pictures menu and tap on it. Of course, this is not that important, since displaying pictures is not the main purpose of the device.
3. Powering off is very confusing: the green led blinks and the device seems powered off, but the picture with iRex remains on it. Sleep mode is straightforward, thankfully.
4. Since the eInk screen can be frozen to an image in sleep/power off mode, can you put an option to choose what picture will it display on sleep/power off mode? This way, I can use the reader as a black and white photo frame
5. I checked folder view on advanced settings and I don't see any difference (do I have to edit something in the .ini file also?)