This is a very good little app for searching tagged files. But I find it somewhat cumbersome dragging and dropping files on its icon in order to tag them, so I don't use it for that. Instead, a better solution for me is to tag files in DefaultFolder X's saving dialog when creating them. For existing files I use another excellent little gem: Tagger. Here is the link to it: http://hasseg.org/tagger/. With Tagger, I simply select any number of files, launch it and tag away! Quick and easy.
Because Tagger also uses the OpenMeta system, you'll be able to search files using Tagit. I don't quite like the idea of having two different application for tagging and searching files. But until Tagit offers an easier, better alternative to drag and drop, I'll stick with both. On the other hand, if Tagger incorporates searching capabilities, it would currently be a better choice in my opinion.