This is just ridiculous. First Expression web is not for developers, then it goes great with Visual Studio (which is for developers), and now they don't do custom controls that aren't signed and installed in the GAC. What the hell? Did Microsoft have ANY idea what kind of deployment NIGHTMARE that would be? What if the people on your team are writing their own controls that are updated frequently. You mean that the designer has to know enough about the GAC to be constantly pulling the BINs from source control and copy them to the Windows\Assembly folder? Have they not ever dealt with Assembly Hell before?
I'd really like to see what other component vendors and developers have to say about this. Seriously, I don't know what MS is smoking over there, but this whole Expression Web thing is really starting to feel half-assed. I never thought the DevDiv could botch something this badly.