I just put my one on tonight (I can't remember exactly who I got it from on ebay, but I had 4 for 2.49 so I don't think it was the same seller as the link above).

Size - About 99% correct. I found it just going into the edges a little bit too much, so I have some bubbles in some places around the edges. Maybe it was 100% perfect fit but I didn't do a 100% job of fitting it!

Response - I've not noticed any difference in using the screen via finger or stylus since I've put it on.

Brightness - No great difference, to my eyes at least!