The Visual Studio blog has a post on how to re-enable thumbnail preview in Visual Studio 2010 RTM.
I can't see why thumbnails in a text editor are compelling, myself.
Here are three thumbnails I took from text files, using Visual C++ Express 2008's Ctrl+Tab dialog:
The first thumbnail is C# code from a file transfer program. The second thumbnail is C++ code from my POKEY emulator. And the third thumbnail is from a Persona 3 walkthrough.
Thumbnails are useful for images, but text files aren't terribly distinguishable in thumbnail form, especially when they're all from the same project and same language.(Read more....)