I have one running my 120 GB Seagate and my 160 GB Maxtor. There is no noticable difference in transfer rates or access. Works like a charm. There is a diagnostic self-check or something when you turn your computer on though, it just checks to see what's connected to the PCI card, so it slows your boot down a little bit, but it's all good overall. I have a 20 GB Western Digital, 80 GB IBM, 120 GB Seagate, and a 160 GB Maxtor, all 7200 RPM. They all work together like a team