the OS/firmware probably lacks DMA which wouldn't helpthe DSL-502T(which I've got) runs linux on it, and I've now ported it to OpenWRT, and I remember reading some where that they don't have dma, or at least dma for usb working yet
Don't. Further reading has revealed that this class of device has extremely low throughput (over both SMB and FTP) - in the case of the DI-624S, only about 500k/sec. Newer devices, eg. Asus WL-600g, still deliver less than 2M/sec. About 5min to download a 512Mb card.
