Google's new found interest in Google Reader hasn't stopped at the redesign that it unveiled not so long ago, to quite a few criticism it has to be said. Reader is getting a Labs section of its own, titled Experiments and only holding one feature for now "smooth scrolling."
Once enabled, the feature adds an animation to switching from article to the next, most noticeable in the expanded view. It's a small visual improvement, but one that makes browsing your feeds a bit more pleasant.
It adds a certain delay to moving from one item to the next, it's not a lot but it is noticeable. In most cases, the trade-off may be worthwhile, but if you emphasize speed and perceived responsiveness above everything else, this feature is probably not for you.
Google has also been tweaking the design after the initial roll-out, it's been adding more colors for one, as you can see in the image below.