I've never tried it before, but it seems to grab my disk the first time, then it makes copies of changed files. My used amount on the Mac is around oh, say, 80GB. A tiny smidgen now, but thanks to Final Cut Pro...

Maxtor's don't have the greatest track record on reliability. Generally it's worth paying for quality on computer hardware.

I would recommend getting the 2TB version of a MyBook from WD if you can. I think you get more value per gig that way, although I haven't really calculated it out. Besides, it's 2 whole TERAbytes, dude!

But I hear the MyBook isn't very good in terms of working.

What did you hear/read, if I may so bold as to ask?

http://reviews.cnet.com/hard-drives/western-digital-mybook-premium/4505-3186_7-31793438.html
User reviews seem a little low.

They are mostly "whining" about the speed. Personally, I care less about the actual speed. I would rather have all that space. Besides, I have used WD drives for almost a decade and I have some of their older hard drives from way back when that still work even to this day with no corruption or anything. Sure they sound a bit noisy but they are 10+ years old.
YMMV and all that. Go with what you prefer because it is your money after all.

I had a pair of WD hard drives die on me but that was back in the megabyte days and WD are still around so they must have gotten better. I've had nothing but good reliability from Maxtors

I've been using the 500 GB WD MyBook for backup for about 2 years and it's worked fine. Transfer speed is on the low side, but reliability seems fine. I've also never had any issues with the 5 or so WD drives I've used over the years.