It's not slower than web CVS access at Sourceforge. But we aren't interested in that as much as in the checkout/update/commit times via SSH which are about a third of what they used to be at Sourceforge.
Besides, Sourceforge has been announcing that they are "preparing to plan to beta test" Subversion support for several years now. Since Subversion is perfectly stable and whole bunch easier to install and manage than cvs, I really wonder what they need to prepare for.
They obviously have a working set of servers with a working authentication system. Subverison uses exactly the same services and technologies as cvs does, so if they have cvs running, they really only need to install one rpm to have svn running, too. For some reason, however, this seems to be really complicated.
I do not doubt that it requires an awful lot of work and many months of planning and development to get a site such as Sourceforge up and running, but that work has already been done a long time ago. The amount of work needed to add Subversion to that working system is quite ridiculous compared to that.