I have the VST internal burner for my Wallstreet, which is I think just a bit thickier (duh) and slower (4x vs 8x) than the model for Lombard & Pismo.
It works great - burns fine in iTunes, the Finder, Toast, etc.
I love mine, but if you have a Pismo, why not get a Firewire burner? It'd be cheaper and faster. Sure, it wouldn't be built-in, but at least you'd get to keep when you eventually upgrade to a new Mac.
Depends what you want it for, I guess. I originally got mine to back up important data while on the road, but since then Firewire drives have gotten so cheap and massive that they're the better choice for backup. And for burning music, it works well, but having an external model would still be a good idea (since you could do disk-to-disk copies).