Well, there's a question of whether the GPU has to be fed fast enough. My CPU is nominally rated at around 150-200 gigaflops. My GPU is rated at about 5 teraflops. That's about a 30x speed difference (and there are obviously faster GPUs out there). That's enough to move me from compute-bound to IO-bound and make things a lot faster. Once I'm IO-bound, I'll obviously see no more performance increase, but I figure I'll get a good 5-10x before I get there.

Right now, code runs anywhere from a few seconds to overnight, depending on what I'm doing. I'll also mention I'm working on many projects, so that's not overhead I incur every day, just once in a while.

Moving to GPU would move that to running anywhere from more-or-less instantly to an hour, I figure, based on similar very back-of-the-envelope benchmarks and guesstimates. That's totally worth dropping $1000 on a new GPU, if that's all it took and things worked out-of-the-box. It'd pay for itself in a few programmer hours.

On the other hand, that's totally not worth weeks of programmer / dev-ops time for switching to a proprietary tool chain. An alternative there is to wait for my computation, or to optimize my code. Both of those seem cheaper than maintaining a GPGPU workflow, where GPGPU is right now. If GPGPU came batteries-included in Ubuntu+numpy, it'd be an entirely different story.