John Jacobson provided this tip in the Delphi Newsgroups. For some people this works, for others it does not resolve the sluggishness when switching between forms.
Posting #1 I think I might have solved the problem with delays when switching tabs in the editor. It seems that turning off all three options in palette properties for showing Code Snippets, "Always Show Designers" and I forget what the third one in that group was, seems to have fixed the problem on my machine. Now I can switch from tab to tab as fast or even faster than in D7. Is anyone else able to reproduce this? I have D2005 Pro running on a Celeron 2 GHz, 512 MB RAM. JVCL, TMS and a bunch of other stuff loaded. Also, I'm running Delphi as trimmed down through a DCM set (Win32 only, no Together, Calibre, etc.)
Posting #2 Right click on Palette, choose Properties, then Options|Tool Palette|Features. Uncheck all three.
Jake was referring to these three options: "Show Palette Wizards", "Show Code Snippets," and "Always Show Designer Items."