It's somewhat complex knowing how best to scale and crop images when you have many thumbnail sizes, and the images in question range wildly in size and dimension, from square papers, to long, thin ribbons.
I've worked on this previously, but Marisa and I still weren't happy with how thumbnails were being cropped for some images, so that you couldn't see the full image very well. For example, check out this screenshot of the front page from earlier today: http://i.imgur.com/EZXD7.jpg
Anyway, I spent quite a lot of time today improving the system (which I wanted to do before our new designers came on board): we now have nearly fifty image styles, and several switching mechanisms that scale and crop images differently depending on image dimensions and ratios. Here's the end result for that same front page screenshot: http://i.imgur.com/StvhD.jpg
Now you can see what that word art actually says!
Because of CDN and browser caching, you won't see the changes right away (the front page might still look like that old screenshot), but over the next few days you should see a difference...