Doesn't sound altogether out of whack. I just did my first backup with this software and 400 GB took about 15 hours.
I had the pre-scan enabled, and didn't turn off the virus scanner on my servers so I'm sure that I can get it to go a fair bit faster. I am going to keep an eye on them next run to see if it does better.
If I back something up from the server that my tape drive is attached to I get about 4800 MB/Min. On this first run my other servers clocked in at about 400 MB/Min. Since they're all on a realitvely lightly used gigabit switch and they all have decent hard disk arrays in them I think that I should be able to get the backup done much faster. Probably just a matter of tweaking settings.
I am a little stumped myself because the HDDs don't look like they're under heavy use when the backup is running, the switch tells me that it isn't under heavy use either (and no packet loss or collisions)... plus neither CPU (on the source or destination server) is under duress so I am having a bit of trouble determining where the bottle neck is.