Followed road with GPS watch described here: http://jpsuae.com/JPsUAE/Hiking/Entries/2012/11/17_Hiking_-_Jebel_Hafeet_1160m.html
Started at 10.15, reached the peak on the UAE side, near the border fence at 15.15, calm pace.
Needed headlights on the descent. Use GPS track as teh route is hard to follow. Thereare some cairns, but only on the bottom portion of the track until the cave (about 2/3rds up the way). You need to go into the cave below large rock, then turn to the right inside the cave. Not possible to go over the border fence, so when you reach below the fence, scale the small wall (about 2-3m vertical), then turn to the left and go stragiith up to the smaller peak (with the bush on the top). From there to reach the main peak at 1100m, you need to swerve to the right around the peak with the bush, then go stragith up in the rock rubble. then turn to the right and cross through the window to see the main peak. Then go stragith up, next othe ancient (5000 year old!) small huts (about 1 m in height). Remember to take flashlight. For the entire route, from the beginning, do not cross to the right side of the valley all the way up, stay on the left. In one place (at 550m altitude) there is a small pool with a large tree (4m tall), then cross into the riverbed, but stay on the left and go stright up the crack to the left and NOT the riverbed itself!) This route requires medium to high effort, as most of the way is on slopes with 45+ degrees inclination.