In case you haven't heard, the .Net FX 3.5 Service Pack 1 and VS 2008 Service Pack 1 have been released! The VS 2008 Express Edition with SP1 is also available here.
In addition to providing bug fixes, the update also includes a number of new WPF features. One of these is the .Net Client Profile, which improves the setup experience of client applications in both speed of installation and size of the redistributable, reduced from 197 MB to 26.5 MB.
You can read more about the SP1 update on Somasegar's blog.