This is a feature I would love to see, no clue how hard it would be but I can say I for one would use it for every track I have. There is a field for it in the ID3 spec If i recall correctly too.
If your wondering why it would be helpful. I DJ and try to use jaikoz to keep my collection updated and having the actual key of each song allows us to create mix’s that are harmoniously congruent. IE, pleasing to the ears.
Thanks for an awesome job, would be nice if upgrades were a little more transparent too, perhaps from inside of the app and preserved the files, settings and database. last 2 times has been a bit of a "delete a few folders and see if it will now run type of deal. At least on linux it has been.
Again, Thanks for all of your work, bought it the first week I tried it out and have turned quite a few other DJ’s onto it so far.