At least according to the WSUS Product Team Blog.
Originally Posted by The WSUS Product TeamIn addition to the next week’s WSUS 3.0 release, we are making the new client portion available via the following plan to our customers who continue to experience performance issues like UI hang and long scan times.
The new WUA client addresses these issues with deep architectural performance optimizations. Combining the installation of the new client, with the latest MSI fix available in KB927891 available on Microsoft Download Center, will completely address the what we have fondly called the svchost/msi issue. It’s important to keep in mind that the new client is only a partial solution and clients must have both KB927891 and the new 3.0 client installed for a full solution.
On May 1st, a standalone version of the client will also be made available to those of you who need to address this performance issue now. Although this will be immediately available, it will have to be independently distribute. Instructions on how to get this standalone new 3.0 client version are available at - http://msdn2.microsoft.com/en-us/library/aa387285.aspx