My university had a few PS3 clusters. The CS department loved them because you could buy three of them for the price of a good server. The department even offered a crash course on programming for the PS3. I didn't take it, but from what I understand, it wasn't that difficult to program (for the department use cases).

The major use case for these was for number crunching (training neural nets, running physics simulations, etc). And these things were something crazy, like 100x faster than a similarly priced PC server. There were plenty of libraries out there for doing linear algebra.

A quick google search suggests that this was extraordinarily common in academia. I found materials from lots of different universities that were close to what I remember my peers talking about.

This was also a little bit before CUDA hit. So there really wasn't a mainstream offering for doing massively parallel, SIMD calculations.

Edit: I went to Wright State Uni and most of my CS professors did research associated with the Air Force, which as forgotpwd16 notes, had at the time a super computer made from PS3s. This might explain why the PS3 was so popular among our department.