I tried out about 250MB and was done in about an hour.Yeah that's the problem with a lot of consumer broadband connections; most have a very low upload speed. If you have less than 1 Mbit up, its going to be painfully slow.
Not sure if I will try the unlimited to back up 160GB. At these speeds I figure that it will take close to a month to do the initial backup.
On a side note, does anybody know how secure and reliable this service is?