I picked up the serial->usb cable from radio shack. It's one of the more expensive options, but it seems to be high quality and so far it's worked flawlessly. I connect to a Win7 VM on my Mac.
I love my 2.5 SE. Makes a huge difference.
PROcede Rev2.5SE // aFe Stage-2 PRO Si Intake // BMS OCC // SmartTop
If I wanted a slow convertible, I would have bought a Seabring.