The basic facilities are fine - everything is new and shiny. The staff mean well and clearly want you to enjoy yourself. The breakfast is, indeed, solid as the other reviews point out.
But all of the little touches that make a nice hotel truly great are lacking. There are many examples, but here are a few: few staff speak a second language (we speak English, Spanish, French, Portuguese and a few others - we would've been fine with any of these), and they seemed thrown off by pretty basic questions; wake-up calls were late; you can't make outgoing phone calls from your room; the TV is about 5 meters from the nearest place to sit, which basically renders the TV useless; the shower floods the bathroom floor every time you use it; etc. Each of these things isn't consequential, but the sum of them is - it meant that we were uncomfortable the whole time.
This wasn't what we'd expected - we saw that it was a new, fancy-ish cave hotel and had higher expectations. In retrospect, maybe that was unreasonable, but it does mean that I wouldn't recommend this hotel to others looking for a luxurious experience. (To be honest, luxury didn't seem to be a feature of Cappadocia.)