Agreed. I haven't subscribed yet for my 8gb iphone 4. But thinking of getting a 16gb wifi iPad for my wife's birthday. At that point I will likely subscribe. We have about a 40-50gb of music. only about 300+ songs were purchased from iTunes. The rest was either ripped from my CDs or purchased from Amazon.
It will be nice to have access to all of my music (granted not all fits locally on the phone at one time).