I went to Hidden Valley twice last year for the first time, and its a decent place. Its only got like 13 runs or whatever, but considering there are no lines, and no crowd, its well worth it. Also it was warm enough to snowboard in just some snowboarding pants and a t-shirt.
I had a good time both times I was there. The snow is pretty much 100% man made, but dont let that scare you off. The terrain parks are pretty sweet with some nice jumps.
One thing to keep in mind, like most resorts, the food at the place is super high, like 3 dollars for a small bottle of gatorade, 6 dollars for a burger etc. The parking lot is really close to everything, so i would suggest packing your own lunch and leaving it in a cooler in your car or something. I will be going back this year for sure...if they get it up and running.