There are some reviews here that are missing the point of this product.

If FileMerge and/or commandline tools will meet your needs then, by all means, use them and save yourself a few bucks. But if you need some more advanced features, Guiffy is a good, professional product. In my case, I bought it for the graphical three-way merge.

Sure, it's implemented in Java and looks it. But this is a tool for getting work done, not sitting back and admiring the Core Animation transitions. When you're drowning in 12 variations on the same codebase (what were they smoking?), as I was, the java-y controls won't bother you at all. You'll be too estatic that what seemed like a difficult, error-prone, weeks-long process of updates and verification is actually going to be a short and simple task. There's nothing like using the right tool for the problem, and Guiffy is that tool when FileMerge, et. al. aren't enough.

(Note: I used the previous version, but I did not experience any problems with an earlier update, so I'm not too worried about 9.)