It took me about 30 minutes to get to the top of the trail and another 10 minutes all the way to Big Bhudda. I did the ascent in the middle of the day and it got quite hot, so be prepared and bring some water. Did the descend just before sunset and that was a bit easier and quite a bit faster. Its slippery though.
Like other people mentioned, use decent shoes. Also there are some electrical wires which you should probably avoid.
All in all, nice little adventure.