I tried backing up a laptop one time with a measly 80GB drive using USB2.0 and it took me hours.
All laptops should have an eSata port, especially if you've got a 200GB or bigger drive, otherwise you'll be waiting HOURS for a full system backup to complete.
Of course, it all depends on HOW MUCH data you need to get backed up.
Hard drives simply suck at backup, they are slow when it comes to transferring their full capacity and just as useless when it comes to having a backup that is durable/removable. Tapes are still the best way to go, they stream fast but have limited capacity and the drives are very expensive.
Tapes need to come is 1TB capacities, they should cost no more than $100 a pop and the drives should be selling for no more than $600. I would not pay anything more for a tape system for home use. The problem is tapes are still targeted at businesses, which can easily pay the $2000+ price for the best drives.