I used TableNinja when it was in the testing phase for FT, but haven't since upgraded and bought it. It is an amazing piece of software if you're multi-tabling, but if you're only playing 4 tables, then don't waste your money on it. I will buy it down the road, I just haven't been putting in my normal volume as of late so right now I have no need for it.
I also have LeakBuster and like sly said, it will only be valuable to you if you're willing to put the time in to it and learn from it, which I imagine many people will do right when they get it, but then won't touch it again for a long time.