I have over 11500 tracks on my iTunes. I would consider myself a hardcore iTunes user and I rate this product.
Yes, it adds comments but I find that useful. It adds a date and often I find myself checking the comments to see if I have not forgoten to run iVol on a particular album.
I would say, 98% of tracks are now at a good volume. A few slip through somehow. they are adjusted but due to a quirk in the track are not quite the same level. However, its a million times better than the iTunes method! So what have you got to lose?!
I set mine to 93dB, single song mode and it actually lifts the volume of some old quiete tracks.
I love it and I dont muck around or allow any dodgy programes anywhere near my imac!