I recommend you all get it, I discovered it yesterday when I installed windows 7 (which btw, is a massive upgrade over vista).
What it does is it places (quite literally) a thumbnail next to any link you hover over. By hovering over the thumbnail, it automatically generates a new, much smaller, pop window to allow you to preview to link.
I find this is a very useful tool for some of the longer fanposts, when you only want to read a few new posts. It allows you to see what others said without dealing with all the clutter.