I installed WSS 3.0 and pointed my TFS2005SP1 installation at it. I am planning my TFS 2008 upgrade. Everything I've read mentions migrating to WSS3.0 after the TFS upgrade.
Are there any gotchas I need to be aware of related to the WSS upgrade already having been performed?
I am in this same situation. I have TFS2008 sitting here ready to go. What I am ultimately thinking is that since Microsoft did put out official documentation on how to upgrade TFS2005 to use WSS3.0 (which I followed and worked perfectly), that the upgrade from TFS2005 to TFS2008 should go on without a hitch with WSS3.0 already in place.
I am still a bit nervous about it and your question is the first mention I have even been able to find online about this.
I had issues with the upgrade. It would always silently exit after entering the Reporting Services account information. The next page of the setup wizard is supposed to be SharePoint connection settings. When I upgraded, I did not replace the WSS 2.0 site but installed side-by-side and changed the SharePoint port settings in TFS config. I think this was the cause of the install failure.
I ended up building up a new virtual machine with the exact same specs, computer name, etc. I did not install TFS 2005, but restored the TFS 2005 databases and then ran the TFS 2008 installer. It detected and upgraded the 2005 databases and all is well.