This works perfectly in Oleg's firmware 1.9.2.7-10. I have partitioned it with:
128 MB FAT32 for the Archos firmware, 128 MB swap (which I never really need), and the rest ext3fs for /opt.
With WL500W-1.9.2.7-d-r1000, the device is only detected the first time. If it is powered off while plugged in, the device won't be detected on that port unless the router is restarted or ehci-hcd is unloaded and loaded again. I have documented the issue at http://code.google.com/p/wl500g/issues/detail?id=76