Same question as to Mana: what did you use it for?
To learn how to create multi-threaded, multi-processing parallel apps on a processor like cell. Processing and transforming large data loads. There weren't many ways to be able to experiment and learn on a system with as many cores as cell and it was incredibly cost effective as a learning platform. You got access to 6 of the 7 SPE's and could create applications that did a lot in parallel.
I got my little piece from the class action settlement. It is what it is.