Most of the full text search interfaces for software packages has been useless. They take a lot of memory and when you search for simple terms you either get a hundred false positives or no hits at all.
That does not mean the idea is bad, just that the problem lies in its execution. Make it nimble and make sure you have everyday use cases, and that you do it well. It's may not be a very rock star programming problem to solve, but as Google has showed, search can be a very useful user interface.