Same problem here, but using a Sony Vaio laptop with and AMD graphics processor.
The start screen tiles were sharp before the update to 10586, but since the update, the tile contents (icons, live-tile stuff) have become blurry. This isn't affecting the text on the bottom left of the tiles, just the text and images within the content.
Just had a test and it appears that the tiles only appear blurry for me at 125% scaling. 100% and 150% are nice and sharp. Irritating considering 125% is where I need it to be.