i've used WhereIsIt for some time but if you're not going to buy it,you better try some other app.(or find yourself a properly craked copy)
now I've stuck with Pirem CD Cataloguer..it's far less powerfull than WherIsIt , but the good thing is that it can take a preview of your mp3s (no ogg/ape etc..

) , so if you have a lot (i mean LOTS) of mp3s it's a good one...
anyway,I'm still in search for tha perfect (e.g. cross-platform, cross-format, modular and preferably free) app ...
if i was a programmer i was going to write one myself