Yep I'd say worth an afternoon – I ride there reasonably regulary (parent's live nearby). If you park at the cycle centre the main DH & XC loop are pretty easy to find.
You could always ask in the cafe/miserable chap in the bike hut if you can't find the tyre tracks to follow.
Last time I went I did a quick run of the XC loop and it appears to have had the start point changed (was a bit confusing as it was muddy mush) and they've dumped lots of gravel down, I'd assume to help prevent erosion but it's also covered over a lot of the technical rooty bits. Bit disappointing.
The main DH is quite nice rooty/rough. If you push up past the fireroad there are a number of other smoother more jumpy tracks above it which are good fun.
Oh and last time I went a saw 6-7 wild boar which was a first!