I set the software to backup my WHOLE drive (from the C: directory down, with no exclusions). That's about 208GB of data. I've left it running overnight and over a day at work, and this is the progress so far.
(I didn't take a snapshot of the other screen, which indicates that this process was started at 12:32 am, so it's actually been running for about 19.5 hours at this point, though it apparently was idle for a while)
That's right: after 19.5 hours of work, it has only backed up about 20 GB of my data. At this rate, it will take about eight and a half days to complete. USB 2.0 may be slow, but it ain't that slow! The whole time, it's been using between 30% and 50% of one of my CPU cores.
To be fair, it is verifying the contents of all of the backed-up files as it goes. I do appreciate that. But seriously!
To ensure that it wasn't a problem with the drive, I copied my 1.3GB Guild Wars data file (a single file) to the drive. That took 1'09". I copied my nearly 8GB Unreal Tournament 3 install to the drive (1900 files exactly), and that took 10'21". Memeo copies files at 2% of the speed that Windows Explorer does. Another way to look at it is that Memeo is 50x slower than Windows Explorer.
I recommend that you don't buy Memeo software. They might eventually get it right, but you should wait until then. Western Digital should find a new company to provide their backup software - this Memeo junk just makes them look bad.