The good old concept that programmers have been using for ages has finally come to designers!
Imagine. You need to find the file with that unmerged effects among the heap of 2mb files which were called hastily 'Untitled1.psd, 'Untitled2.psd', 'Untitled2_a.psd'. And now you have to open every single file, wait for it to load, scroll through it, and then find the effects you was looking for. Sounds familiar?
Now you have another option!
ComparePSD compares two Adobe Photoshop PSD files for you and highlights the differences. Layer by layer. Effect by effect.
Simple.