We've been having performance problems on a new 64-bit SQL Server 2005 cluster in our test environment. We opened a ticket with Microsoft to assist us with this.
After modifying several things, the only thing that was slow was Management Studio. On both nodes of this cluster, it would take about 3-5 minutes to load Management Studio. The first MS engineer suggested that we add the nosplash switch to the Management Studio shortcut, like this:
This did not increase performance at all on either node. The second MS engineer suggested that we uncheck two options in Internet Explorer's Advanced Security settings. The two options are "Check for publisher's certificate revocation" and "Check for server certificate revocation".
After restarting both nodes in the cluster, Management Studio took about 15 seconds to load the first time and 1-2 seconds for each subsequent load!
So if you are experiencing similar Management Studio slowness, I'd suggest trying these out.