If I had loaded 5,000 tracks instead of 1,700 - I might never have liked iTunes. Seriously. Eight minutes is twice as much evaluation time as I usually devote to 'new' applications. There's simply no way I would have struggled through 20 minutes, or God forbid, an HOUR. I don't think anybody would have a favorable opinion of iTunes if they used it during 'sound level normalization'. Heck, try it yourself. I bet the word 'snappy' doesn't come to mind, to say the least. Apple sincerely needs to mention the (temporary) penalty for enabling that 'Sound Check' box. Better still, they could lower the priority of the process that scans the media and sets the average sound level. That would allow most other tasks (those set to normal priority) to override the priority of the 'normalization process' - which would eliminate the sluggishness at the expense of taking longer to 'normalize'. In other words, the negative effects of 'normalization' would be gone - but you would have to wait longer (initially) for the benefits.

Again, iTunes for Windows is very impressive. It HAD to be, really. Even if took forever to create it.

But if I were Apple I would work on that 'normalization' issue. For example, my Sony OpenMG Jukebox software locks the window until sound level normalization is complete. While this seems a worse solution than allowing the user to continue doing other tasks during normalization - it certainly prevents the user from perceiving that the software is slow and laggy.