I honestly don't know why some people seem intent on complaining about this. either they've not actually used it. Or in the case of at least one review they arn't complaining to the right people (check the sale of goods act if you are in the UK being fobbed off back to Sony is simply wrong).
1, Yes it does flash bleck to white between pages. This takes about half a second. far quicker than turning the page would be.
2, The screen is somewhat fragile. But to actually break it isn't "easy". I've had mine well over a year and it lives in my cargo trousers on a knee pocket 99% of the time. I read for 3 hours a day on tube and trains, and have never yet damaged it.
However there are 2 things which could cause the screen to break. One is the glass substrate and when this goes it's usually quite obvious as you can see them It looks jagged.
The 2nd is the display controller.if that goes then it usually produces a line or a square to dissappear or turn black. You can usually tell this isn't a broken "screen" because it's perfectly square and inline.
Examples can be found by googling for the "prs505 forum" (heck even using my nickname will get you there). If it's the latter this is a hardware issue and should not be charged by Sony.
The 3rd complaint I have read recently is that it doesn't support all formats... This is true, but I've yet to find an ebook in one ebook format that isn't available in another. And it _does_ support the most common formats (epub).
Worst comes to worst, there are numerous bits of software that will convert formats for you (calibre for example). Not to mention there is a huge ammount of (legal) free content such as the Baen website.
Lastly the complaints about PDF support. It is true that many PDF's are all but unreadable. The reason for this is that PDF is a print format. So if it's designed to be read on an a4 sheet it will almost certainly be less readable on a 5 inch screen. On the otherhand a PDF designed for an A5 sheet is perfectly readable. And "reflowable PDF" is also fine. so what I am saying is if you _pay_ for a PDF that isn't readable you should complain the the people who produced it as a minor tweak from them will fix the problem.
As I've said I use this on a daily basis. I read for a minimum of 3 hours a day. This device is as comfortable to read on as paper. I used to read on a PDA and it gave me headaches due to bad contrast, & flickering. These do not happen now!
The battery life is enough that I can read all week before I need to recharge. Longer if I shut it down completely between uses. And it uses the same charger as a sony PSP, or sharp zaurus, and will charge in an hour from that (and you can read while it's charging from the mains).
It's not perfect, but my quibbles are minor. So I've given it a 4 star review.