I just bought a Rosewill Expresscard 34 device for my macbook pro and is hooked into a 7200 rpm 500 GB external. Well, I installed the driver for this card and was trying to transfer about 40 GB worth of data over to it. It was transfering in "spurts" and took about an hour to transfer the data over. There are lights on my card and they only blinked for about a few seconds at a time, meanwhile the status bar crept slowly across my screen.
I've read that the driver that comes with the RC-605 (Sil132_1.1.9u_Sil) may not be compatible with Leopard 10.5.5