I have a fairly large ASP.NET application that has a large number ASP.NET WebParts built as Custom Controls (150+) in a compiled assembly . I've been getting a little annoyed with VS.NET (I'm using 2008 right now, but saw the same behavior in 2005) where after I get done compiling I have to wait 20-30 seconds while VS.NET does ?something? and freezes the UI (can't ?someting? this be done in a worker thread). Anyway I think I've finally figured out what's up, it would appear anytime I open anything that requires a designer (including an ASMX page) the tool box get's populated with all the custom controls as part of my project. It would seem as soon as the tool box is populated it needs to be refreshed and that's what's taking the 20-30 seconds. So therefore if I don't open anything requiring a designer, I'm OK. I think I've gotten used to this for ASPX and ASCX pages since they normally open up in the HTML view, but I'm still clicking on ASMX and Services design surfaces and end up shutting down VS.NET and restarting without a design surface open.
Maybe my project isn't typical, but it sure would be nice if I could use design surfaces at some point.