I visited the Preah Vihear Temple during a trip to a few weeks ago during a trip around the eponymous province.
My visit took a unconventional route. I took a wrong turn and ended walking through the army encampment at the bottom of the grand staircase. Fortunately the officers that I met were congenial and after sharing of cigarettes and beverages, became quite friendly. Having a view sympathetic to Cambodian ownership of the region (fairly easy) and understanding the hardship of jungle warfare (more difficult to pull off) was helpful.
During my climb to the top, I did not see any tourists and I had the place more or less to myself. After admiring the view from the cliff top, I made my way to the central temple. The actual temple structure is a ruin (bit like Beng Melea) but the sanctuary remained intact. There I saw something that really made my visit. A large party of locals sudden appeared and took part in some ceremony with the monks. Very mysterious, romantic and poignant at the same time.
I will forgo a detailed description of the site other than to say that it is in poor condition and what remains, in my view, is not that amazing. If you happen to be nearby, then certainly take the time. However if you are in Siem Reap or Phnom Penh, then I do not think it would be worth the time and effort. Perhaps spending the extra time in Koh Ker might be a better investment.
I should reiterate that although there is no entrance fee, a passport is needed to register at the base. Also it costs $25 to hire a 4WD from the base to the temple.
