There's something going on with this site too IMO. Posts have slowed to a trickle and have become very sporadic.
Like you I think most people have enjoyed a very enjoyable Optus cable experience for the past decade or two. Congestion just wasn't a word anyone new. But the confluence of the factors I mentioned suggest its struggling. Its my suspicion that once the NBN is on the horizon for an area Optus are cutting corners. Saturated nodes have more customers added to them. Maitenance and upgrades stop, etc. Its just a theory, but Optus aggressive policy of shutting its networks down completely just three months after the NBN arrives (instead of 18) supports it.
Regardless, what once was good appears to be falling into decay and as long as its not completely broken, OPtus appear to be quietly backing away from it.