yes i have been there a few times and know it, walked it from different start points, from New Radnor there is a dead end road that rises very steeply and ends at the wood at 'Whimble' and there is a car park at the end of the road in the wood, further down the main road A44 there is a track that ends in a car park by a waterfall called ''Water-Break-its-Neck'' and you can walk from there (some nice big trees by the waterfall) going either left of the big wood ''warren plantation'' and up over the summit ''Nyth-Grug'' or along the track beneath Nyth Grug, or go right of warren plantation and walk up through ''Davey Morgans Dingle'' which is nice (the streambed in Davey Morgans Dingle can sometimes dry up in dry weather), you can approach from the north through the forestry from the A488 at ''Bledffa'' walking up through ''Rock Dingle'' or ''Fishpools'', if you have no transport you can catch a train to ''Dolau'' and easily walk from there approaching from the North West through LLanfihangel Rhydithon. There is a large steep-sided valley area called ''Harley Dingle'' which is a firing range and often closed to the public and it sits beneath the areas highest summit which is ''Great Rhos''. At the summit of ''Black Mixen'' there is a radio-transmitter aeriels and workers buildings but there is a nice viewpoint there on a spur looking all down the steep Harley Dingle valley. There are some short rough cliffs called ''Whinyard Rocks'' which attract various birds and on the top moorland around Black Mixen/Great Rhos Hen Harriers have been seen. The area at the head of Harley Dingle where the stream meets the wood at a place called ''The Riggles'' can be quite boggy in and around the wood there, there is a place there called ''Shepherds Well'' but it is no more than a tiny spring which sometimes completely dries up. If you walk from the car park in the Wood above New Radnor walk North alongside the wood on your right going past Whimble Hill then Whinyard Rocks heading north to Black Mixen summit you get a lovely view of the Bach Brook gushing down the steep valley, then contour around the summit of Black Mixen taking in the lovely view of Harley Dingle from the spur earlier mentioned, then onto Great Rhos summit and descend down Davy Morgans Dingle ending up at the lovely waterfall Water-Break-its-Neck. The forestry around there is mostly conifer plantations but there are some nice trees by the waterfall. Do you want to know anything particular about the area.
PS to Harvestman, the area is VERY accessible, by foot by car and by train.