Supposedly it'll take some things in the Surefire P60 module format. Don't know how hot you can go though since it's plastic. There's a luxeon drop in that's been reported to work fine.
We're talking another $30 for the drop in, and you can find some nice cree flashlights for the same total, e.g. a Fenix P1 CE or a Lumapower LM303.
I have one with a dealexteme cree module in it. costs $11-15 and fits with a little filing. i have beaten the crap out of this light and it still looks and works fine.