Use-case scenario:

A group of software developers works a lot with Matlab models. To auto generate code they need to be able to set a different diff tool for those files. Even Excel files are used a lot for different reasons and FishEye doesn't seem to be able to diff those either.

It would be nice to at least be able to open them both in Excel and diff as you can in Tortoise SVN for example. Alternatively, to have the possibility to change the diff tool per filetype or any other convenient way to diff non-text based files.