The New Look of StumbleUpon
Apparently right now you have the ability to go back and forth between the new “beta” version and the old version but soon that will all change and the new interface will be here to stay.
In the old version after you stumbled on a certain website you liked or disliked it would be added to your profile as a thumbnail image - with so many thumbnail images this created a very cluttered view. The new Stumbleupon limits the amount of thumbnails to about 10 and then instead of thumbnail views you have a little larger image of the website along with what your comment was. Compared to the old version where you had to click on reviews to see the review you gave it.
I wanted to give props to the new Stumble interface - if you have not seen it yet - check it out.
Source: http://www.semplistic.com/articles/the-new-look-of-stumbleupon/