Rode HF for the first time this weekend. Sunday in August the place was almost deserted despite mild-ish temps (was about 82 in the morning, 90 when we left mid afternoon).
I really enjoyed it, fun mix of trails. Fast and open, tight and tough, sandy, rocky. Singletrack stuff was nice that it's well marked and directional, and no worries about coming around a corner and some gigantic SxS blocking the trail. We did most of the South Loop singletrack, and a fair bit of the North Loop. The North one is definitely a little tougher. The ATV and jeep trails are a nice diversion if you want to take it easy for a bit, even the higher difficulty rated trails shouldn't be overly challenging for a moderately experienced rider.
Staff was friendly and helpful to us newbies. The harder rated ATV trails and the singletrack was decently challenging, but no crazy hurt-yourself stuff. The few truly difficult sections all had bailouts or bypasses, and generally a warning sign beforehand.
I can see the place getting pricey quick if you want to bring friends or make a weekend out of it though. They have a lot of nice accommodations, but their prices for camping, cabins, and rentals certainly reflect that.