Code Compare Testimonials
Best code diffing tool I've ever used. Ability to edit the current version directly in the tool is great both for easy reversal of changes as well as for formatting, as is the case when diffing poorly formatted code (e.g. single line XML documents).
This is a very powerful tool, and it integrates well with Visual Studio. The more I use it, the more flexible I find it to be. It lets me edit the code on the fly in the difference window, and even set breakpoints. It's phenomenally better than the native diff in Visual Studio.
Martin L. Shoemaker