I've ridden parts of it at weekends when it's not being worked on. So far it's pretty good, the rock gardens are stupidly steep (TV didn't do it any justice) but there are bermed sections next to the rocky bits for the less suicidal!!
There are now 2 tunnels by the looks of things where as the Olympic track only had 1. It has been expanded and loads of extra bits added. It's pretty vast, with new bits added to what was already a public section of parkland. The 2 downhill stone bits in the photo look pretty mental and are very steep. There is a new multi million pound visitors centre currently under construction so all in all it's being taken pretty seriously. It will probably end up being a pay to ride facility, but how they monitor that will be interesting!