Yeah did it with my girlfriend a couple of years ago. It's a nice ride with some slightly techy bits on the section next to the reservoir – at least it was back then due to the bridleway being very washed out, it might have been repaired.
One tip – at this point;
http://www.streetmap.co.uk/map.srf?X=310362&Y=219120&A=Y&Z=115
make sure you go under the bridge and carry on down the bridleway rather than ending up on the fireroad as I did first go!
Depending where you are coming from, if Brechfa is in range then the green/blue route there is another place that's easy enough for a less confident rider but bags of fun for you too.