It's a Toshiba drive internally. Rumor at the time was that the 360 Elite would have the HD-DVD drive built in, but that didn't happen. The external can't run 360 game discs, just movies.

When they went on fire-sale I thought it might be useful for having two games available to run on the console at once. I'm glad I didn't pull the trigger on that.

Loading times were bad enough from the internal drive, I shudder to think how bad they would be when streaming data in over usb.

I still have a couple of HD-DVDs but not that drive any longer and if memory serves me right, I was able to connect it to a PC and play a HD-DVD movie in mplayer or something

I bought an XBox HD-DVD drive expressly for the purpose of, err, "preserving" my movies once the format died. It works well connected to a PC.