Again, new at it, so I'm sure someone can give better input than me.
There seems to be a decent DH scene, usually see 2 or 3 shuttle run groups out at Fox on the weekends, provided it's not miserably hot. Don't think heaps of people ride the Eagle On The Hill DH Track, don't exactly know why, but I think it's not meant to be a great track and it's a prick to get to the top of when the gate isn't open.
Shops for buying bikes, or just gear, servicing etc? There is a shitload of bike shops here, but they mostly stock road / XC / road bikes. There isn't much in the way of DH bikes though, some Specialized, Giant, Trek and Intense, but not much else around. The service though is good, plenty of shop guys ride DH, so they know their shit, and can get whatever you need in. I use Trak Cycles in Norwood since I'm friends with one of the mechanics, and they all ride DH.
I think the local series starts up again soon'ish, like in a few months? The series covers a bunch of extra private courses that you wouldn't get to ride if you weren't competing, without jumping someones fence.
Best vague info I have anyways