This is true... but 9MB about as fast as I get and you've heard others say 7MB is also IDEAL just like a 12X CAN do the full 12X. You also are adding seek time of the drive to latency in the network and the entire subsytem of the computer and the xbox... through the pci bus, blah blah blah. So if the moon is aligned with jupitor and you have a completely idle kick ass machine and a completely dead network with good quality hardware then you might get optimal transfers and "seek" times. Also that is 9MB on large files.. it's MUCH MUCH MUCH slower with the smaller files due to all the handshaking that takes place... I forget what we averaged my buddies back up(several games) transfer at.. but we took the total number of files and divided by the size of that total and got the average size of the file we then found how fast on average that file tranfered (I think it wasn't good 2-3mb at best) and used that number to divide of the total size of the backups and it was gonna take x hours... we ended up being pretty much right on the money.
so seek times over the network involve lots of overhead depending on the size of the files.