Recently our team released a service release for Silverlight on 1-Sep-2010. We affectionately call these “GDR” releases (general distribution release).
NOTE: Other teams have different names for different things. I’m not sure why Microsoft doesn’t have a standard on these things and it’s funny to hear marketing teams argue the benefit of one name over the other. For what it is worth, in my eyes, if it isn’t a major milestone release (or at least a ‘dot’ release [4.0->4.1 for example] then it is a service update. Call it a GDR, Wave X, Service Pack, R2, blah blah.
In the GDR1 release...