Chao Srey Vibol is a little known temple because it is situated outside the enclosure where most of Angkor's temples are found. If you decide to visit it, it's almost certain that you will be alone, which makes the visit truly pleasant. However, don't expect a richly decorated temple, or one that is well preserved, because you won't get it!
Chao Srey Vibel is basically a collection of ruins that are being slowly overrun by nature. There are trees growing through the rocks, they use old walls as a support and you have to get around by climbing over the stones that litter the ground. The temple hasn't been restored, which gives you a good idea of what the explorers must have seen when the rediscovered the ruins of Angkor, and that is exactly what makes it so charming, especially if you like getting off the beaten track!