Snow rides on Burnaby Mountain can be quite fun. You just have to take it slow. Roots can be tricky as they get buried and are very slippery. Going up the Trans-Canada trail is slow and much harder. If there is a lot of snow, it is pretty much impossible to ride up the Trans-Canada trail, there was a period last year when that was the case. The trails up top are usually rideable in the downhill direction. Branches end up drooping because of snow right onto the trail, and you can get quite wet and cold, so some form of waterproof clothing really helps. I think the biggest danger are roots - which may be covered in ice and then obscured by snow.