Did you forget about using the DEVPATH when developing against the GAC? I hear a lot of developer complain about the pain when developing code with GAC components. This is just a reminder to make sure you make good use of the the DEVPATH environment variable so you can point to local builds of your assemblies instead of the ones in the GAC.
Add the following information on your developer workstations app.config file.
<developmentMode developerInstallation="true" />
See the MSDN documentation online for more information - http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconenablingruntimetosearchforassembliesinotherlocations.asp