If you are a current user, I think you'll be happy to see that you can now select components and copy and paste them among models. It's probably our most requested feature!

Speaking of often requested features, you can now select units and prefixes from a drop-down menu:

Mac users are in for a treat. Many have Model Center opened on one screen and Simulation Center on another. With the native Mac full screen support this workflow has been significantly enhanced. And SystemModeler overall looks better in 4.1!