The MATLAB GPU implementation is seriously flawed. For a better approach, see http://www.accelereyes.com/products/compare
That being said, it looks like interesting tech.
BTW, you're profile has me cracking up in how you share your email. I tweeted it here: http://twitter.com/melonakos/status/11101399047737344
Do you think GPUs in R would be useful? We're heading that way with LIBJACKET.