Very much worth it if you go with appropriate expectations that it’s a small area, so lot’s of fun trail centre-surface loops. V smooth – one to ride fast, there’s little in the way of technical stuff.
I’ve parked in the velodrome car park a few times – free if you’re cycling, but don’t know how late it stays open.
Certainly an excellent spot for a mugging, as it’s in a legit shithole part of Manchester, but still statistically very unlikely to happen.
No mud at CV – all weather trails.
From Stockport you could ride through Reddish Vale, then a short bit of surburban roads to the Fallowfield loop, which will take you all the way to the canal which the velodrome is on.