After testing for a quite a while yesterday with the newer client I was unable to reproduce the issue. The main thing I tried was dropping a bunch of random items on the ground and seeing what the effect was. In the video posted by Lars, he seems to run slow after picking up items from a kill in the wilderness, and in the old client I was able to reproduce it when picking flax (ie. Picking up items). I noticed a little bit of slowness for the first couple seconds, but it seemed to go away rather quickly and was relatively unnoticeable.
On a separate note, I did experience a little bit of slowness when screen sharing via skype. My fps remained around 50 the entire time. When I stopped sharing, it all worked fine. Maybe some video software interferes somewhere?
On a third and final note, I've noticed slowness when my internet connection is slow. My fps remains the same, but my speed drops down to 1 mbps. When it goes back up to around 15 to 20 mbps the issue goes away.