When I'm sitting in a hotel 4000miles from home and I'm working on Flash MX, iChatting and listening to iTunes.. I am perfectly content. The 17" is a complete solution.. you buy it and you don't need a desktop. You buy a g5, you'll still need a laptop.
Though, I'm still itching for a secondary display for when I'm at home and the 17" screen doesn't quite cut it.