I've used it. On other cars. Not the xFire. I spray it on lightly, then I'll wipe it down.

I found that if you don't get it hot enough, fast enough it will turn into a sticky mess/dirt magnet.

On the xFire, I just keep it very clean, and if I want to show it off a bit, I use Meguiars Hot Shine Tire Gel. Wipe on, let sit, polish off. Leaves a nice satin black semi-gloss.

Of course, this is only for the plastic bits-not the whole bay!