How reliable are airport disks?

So after moving everything to a wireless-N network with Airport Extreme router I've been really happy with the results, very fast speeds and a lot less disconnects on my macs than by Linksys router. Lately I've been attempting to set up a couple of USB drives as shares by connecting them (via hub) to my router. Everything works fine, I can see the drives and read/write files etc. Occasionally however certain operations on the drives (for example deleting a very large file) can be painstakingly slow and then half way through the delete process the disk connection will fail and then the router just hangs.

I had planned on setting the disks up for time machine back ups, storage of media files, pictures etc. but now I'm having second thoughts because of the reliability I'm seeing with disks connected this way. Perhaps I am missing a vital configuration somewhere? Anyone see this before?

Cheers.

USB will be slower on a Mac < data is sent in packets with acknowledgement > Firewire is data stream so i would go for that as a back up method. Can u rearrange network to share firewire HD connected to one of the Macs? Have a look at McBie's comments here for some good comments on considerations.