My Mother (a crazy-avid world traveler) recently discovered this place; my husband and I've been back twice in a month. It's one of those places I think maybe I should keep a secret lest you all rush it and its prices go sky-high. Just kidding. No real danger of that, as it's just not the same category as its pricey neighbor, the Quellenhof.
The Schloss is great, though, if you want an affordable, quiet, relaxing vacation, nothing fancy... if you want to read by the pool, play golf, go for long walks (in our case with our very large dog), lounge in the sauna and head to the bad for an afternoon. That's what we just did and upon checkout they informed us we'd not been quoted the lowest rate and so our bill was significantly lower than anticipated.
Not to get your hopes up or anything... but how often does that happen?!
Not often.
Note: we haven't stayed in the Avantgarde rooms yet but understand they're renovated and much nicer. The castle room my Mom stayed in was gorgeous. We stay in rather dated and worn rooms near the sauna (not up to my business traveler standards, but perfect with our giant dog). The only down side here is there is no Internet in the rooms.
We love this place and will go back over and over.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC