I'm surprised you have to use the command line to change such an option in an Apple product.

The reason that is a command line is because Apple expects users to not change it.

Yes, it should definitely be in the Preferences dialog!

I'm not that impressed with iTunes 10.. the grey icons are a disaster for quickly finding things; it refuses to play a TV Show I downloaded yesterday from ITMS (not authorized); and Ping is lame.

  Yes, it should definitely be in the Preferences dialog!

I'm not quite sure if it's sarcasm or not. Honestly my first thought when I saw the buttons like this was "WTF is this?!". However, this should not be an application preference! One thing that Apple does (that every company should do) is making choices for the users. Sometimes they're wrong (this one looks dubious to me) but adding settings is the wrong approach to it.

I recently started to use a Windows PC (granted it's XP) again and the number of preferences (e.g. system, Outlook) available is completely insane.

Sorry, that was indeed sarcasm. What's the sarcasm punctuation mark again?

You want secrets.prefpane :) (if you are a mac)

Edit: http://secrets.blacktree.com/

Alternatively you could use an application like Secrets that exposes a bunch of the settings in a friendly GUI sort of way. Already been updated for iTunes 10:

http://secrets.blacktree.com/

Uh, this is the norm for many settings in OS X.