I own both Moodlogic and its iPod compatibility add-on, Devicelink. I agree that it's a great idea to profile songs based on pooled psychoacoustic data, and it does have some great benefits: you can genuinely select a mood, or combination of moods (for example, Upbeat and Romantic) and ML will compile you a great playlist of your songs fitting that description.
However:
1) The database is still -far- too small. I have fairly mainstream tastes, but 45% of my tracks are not recognised.
2) The psychoacoustic profiling system is very accurate, but the ID3 tags are -not-. I once left it to "correct" a couple of hundred tags automatically, and came back to find about half totally wrong (i.e. wrong song and wrong artist).
3) You get the impression, dealing with the Moodlogic people, that they're Ideas People; they're just slightly flaky on the robustness of their system. The stability of the software itself is -poor-.
As a result, I still open Moodlogic occasionally, but it's little more than a "curiosity" app in my setup. I stick to more reliable apps to get my serious music organising done. Don't get me wrong - it's a fantastic idea, which is why I was excited enough to buy it; but I think they needed to be on v3 by now. There seems to have been a loss of momentum with development. I wouldn't buy it again.