We've spent almost a week at Khustain National Park Resort with our little tent. Hiked a lot around in the mountains. We saw a lot of red deer, countless marmots, ground squirrels, various butterflies and heard the wild horses fighting.
We stayed near to the ger camp, used the shared washing/lavatory blocks. Unfortunately we weren't always as lucky to have a hot shower. But on the other hand, the lunches were absolutely delicious every time.
The staff was mostly friendly, but guests weren't priority for all of them.