I love to leave my computer running while I'm asleep! So many possibilities! -- power outages in the middle of the night, cats jumping on keyboards, dogs chewing through power cords -- oh, the wonder of it all!

So, judging by your post, I guess one of my questions is answered: defragging should run faster on my newer, faster machine. That's a relief.

My brother has suggested that it should be possible to work on one physical disk while another physical disk is being defragged. Makes sense to me, if you don't mind the slower performance during the defrag.

He also points out that Linux machines seldom need defragging. He didn't explain why. (Possibly has something to do with that journalling file system)

One final question: do any of these defrag utilities have a "pause and resume" feature?
That way, the user could shut down the machine when she has to go sleep, do the grocery shopping, walk the dog, etc., and then resume operations at a later date (like when I'm watching the Daily Show and the Colbert Report on TV.)