[mgmueller]

Next, my momentary favorite, Sony 900 (aka Daily Edition).

Pros:
- Form factor. As usual: Sony beats them all in their design hands down. I find Sony 900 even more appealing than Sony 600. Elegant and minimalistic.
- It came with a cover (only front, the units back is replaceable to exchange battery). Additionally (and quite unexpected for me, didn't read the description careful enough) it comes with a hard case. This hard case is big enough, to use it with other readers like B&N's nook.
- Improved start screen. You find all you need on a single page: Recent additions, last read, daily downloads, .... All in thumbnail (cover) view.
- Very fast in turning pages. I've never had a problem with Sony 505's (or others) 1 second for turning pages. But Sony 900 (and iRex 800) are even faster.
- User replaceable battery and 2 memory card slots (memory stick and SD card).
- Stylus can be inserted into the reader. If I have to attach it to the cover (like iRex 800) or put it elsewhere, I'm a bit worried about losing the stylus. On Sony 900, the stylus even gets inserted on the left side, so it's additionally protected by the cover against slipping out.
- ePUB. You don't have to purchase from Sony (although Sony is absolutely fine and most of the time even matches Amazon's prices). Sony 900 can be registered in Adobe Digital Editions without any problems. You even (and this only seems possible for Sony units) see both memory cards, not only the internal memory.

Cons:
- 3G, but no WiFi. That's not Sony specific, Kindles for example don't have it either. But still: If a unit is composed for wireless data transfer, I prefer WiFi over 3G anytime. Why not having both? Would be a "golden bridge" for people outside the US, to still use Sony 900 fully functional.
- Frequently checks library for new additions and is relatively slow for that (sometimes about 30 seconds without anything new in my library). A bit faster than other Sony units, it seems. But still...
- Glare. Way better than Sony 700 and slightly better than Sony 600. I don't have any problems with the display, I usually read in good light conditions. But quite a few members complain about it. And iRex 800 (of course I have to admit, in a totally different price range) demonstrates how it can be done.
- Stylus too light. I don't like the stylus of iRex 800 very much either. But at least it's heavier. Sony 900's stylus to me seems way too light. The Sony 700 stylus feels better (but can't be inserted into Sony 900, slightly different measurements).
- No support for Sony's own .lrx anymore. It's probably a good sign, Sony focussing entirely on ePUB. But I have about 300 .lrx, which I bought for Sony 505. You can't even strip .lrx from DRM, so they're more or less useless for future use.

Summary:
To me, it's my most beautiful, elegant and cool reader - out of 14 readers in total. Design clearly seems to be Sony's strength.
I love the form factor (height:width ratio). It fits perfectly into my hand (iRex 800 for me is a bit too wide, to rest comfortably for hours in my palm).
I don't have any problems with the display quality. It's no Sony 505 or nook. But I've stopped to permanently compare all units. I check each on its own and I'm perfectly fine with Sony 900.
For $ 399 it's not the cheapest reader out there. But given it's feature richness, to me the price is absolutely okay ($ 399 for Sony 900 vs. € 499 for iRex 800 in Europe).
I'm not the biggest fan of Sony's eLibrary software. But at least I've got a tool to manage my Sony specific library. I've got 5 Sony readers and sync them all automatically with my library (each of those 5 readers differently).
It's a tough call between the first 3 to 5 readers. But I rank Sony 900 my #1.

EDIT: PDF capabilities:
Sony 900 does have reflow and zoom, so do Sony 600 and 700.
It's great for PDFs. But there's one downside: Zoom only applies for a single page. When turning pages, zoom resets. So, if you for example would like to crop margins via zoom, it's not really efficient. iRex iLiad or iRex 1000S (not iRex 800 for now) can do the zoom for the entire document.