[amsat-bb] lvbtracker (or other) and AlfaSpid rotors?

The Alfa Spid price list http://alfaradio.ca/docs/AlfaSpid_Price_June15_2009.pdf indicates that the az/el rotor alone is about $600 (CAD) cheaper than the rotor with controller. I understand that this controller is a very nice piece of kit, and many are quite pleased with, for instance, its mouse interface. However, that additional charge moves the purchase from the 'maybe one day' to the 'no way Jose' column.

So I'm wondering if anyone has experience with third-party controllers to operate the Alfa Spid rotors. Are they electrically similar to other rotors, or is the proprietary controller absolutely necessary?

73, Bruce VE9QRP