At the NYCFUG meeting last night Sony demoed the XDCAM HD system and the recorder deck they have can record HDSDI signals. This might be one way to record Canon XLH1 HDSDI to inexpensive Media for those people who want something better than HDV but not sure about the other HDSDI paths. A little diffferent than DVCPRO 100 HD tapes.
Of course everything seems to be in the 15K range but the wisdom of Canon putting the HDSDI is continuing to play out

I think it's definitely an option, but I heard that xdcam is compressed to 35Mbs anyhow, so I don't know that you would see that much of an advantage. I could be wrong though.

Is XDCAM MPEG as well... Just less bit starved?

Yep, as a matter of fact, it is HDV in technical terms, but they can not cal it like that because it's not on tape.. Though, the higher bitrate option is better quality, it's still mpg.

Granted it is not uncompressed but think about it for a second. It is potentially higher quality than HDV bitrate, It is non-linear and the recording media is inexpensive. 60 mins for 30 dollars. If I was working on a narrative I would consider it. HDV would be your back-up.