Visual Studio 2008 introduced a document switcher window that pops up when you do a CTRL+TAB. Nice idea, inspired by ALT+TAB application switching but I find that the little previews it shows you are pretty useless. One code window looks like pretty much any other at that resolution. I prefer the previous behaviour of just immediately switching windows.
Sara Ford's excellent series of Visual Studio tips prompted me to restore CTRL+TAB's previous behaviour. You can do this by using the Keyboard binding page in Tools Options. In Tools > Options > Keyboard locate Window.NextDocumentWindowNav and remove the CTRL+TAB binding, then go to Window.NextDocumentWindow and assign CTRL+TAB there instead. Same drill for CTRL+SHIFT+TAB for Window.PreviousDocumentWindowNav and Window.PreviousDocumentWindow.