I've also been looking to update my 650 - even though it is working perfectly, I just like new gadgets.
Today I took the 650 into a Sony store and compared it with three T2's. Under the same lighting conditions, similar fonts and sizes, my screen is just as white as the T2's which really surprised me. Also, when opening a book from the home screen, my 650 with 200 books on took the same amount of time as the T2 with only 6 books loaded, which again really surprised me. Of course I left the store without buying anything. My experience totally contradicts the advertising surrounding the T2, unless the THREE T2's on display all had bad screens while my 650 has a good screen - seems rather unlikely to me - but I couldn't deny what I was seeing for myself.
I then went to WH Smith to compare the Kobo Glo and the 650. Even with the light switched off (yes you can do this on the Glo by a button on the top of the unit), the screen was noticeably whiter, but not by an enormous amount, and opening a book from the home screen was quite a bit faster. The Glo's screen with the light on looked evenly lit to me although with in-store lighting it is difficult to tell what it would be like in a dim room. I was also impressed with the font size variability in the Glo, a slider which seemed to have far more (usable) options than the T2. IMHO the T2, like the 350 and 650 had a large size difference between the smaller sizes which mean I can never get the optimum size for me. With the Glo, I found it very easy to find a good size and weight of font.
Anyway, I think I have finally come to a decision - just cancelled my order for the Kindle Paperwhite and will get the Kobo Glo instead. I wish Sony had come up with something new and exciting this year, but the T2 (or even the T1) just don't work for me.
Anybody who loves their 650 and would like a spare in mint condition, please see my advert in the classified section.