Cycling China to Lhasa recent information

Hello,

We are two Canadians cycling for a year. We are currently in Thailand
and are trying to decide if we want to cycle through China to Lhasa.

All ethical issues aside, which we are still wrestling with, does
anyone have recent information on people that have attempted or
successfully made the trip.

Our concerns are getting more than a 30 day visa, and how much problem
and how to deal with the checkpoints.

We have heard various versions, some people sneaking through the
checkpoints at 4:00 AM, and other versions where people have just "gone
through" the checkpoints.

What we would like is a recent (2004) travelogue.
Thanks for any information you can share!

Cheers,
Celine & Steve