I'm all for shared trails as long as there is sgnage or something to let users know that's what they are and that no user has more right to the track than any other. I think all of the comments on the SYS site say they've never had a negative experience but with multi-use trails the potential is there. I imagine that the same potential would be there for mtb specific trails if they aren't directional. I'm okay with either though.
Hopefully someone from here is attending the Turramurra forum right now and will report back on how that went. I know Grant from Trailflix is attending.