My wife and I spent a long weekend here in the beginning of December 2013.
It turned out to be the best skiing trip we ever made, and not least due to Hotel Maribel.
While "only" 4-star superior, they have truly a 5-star services and natural attention to detail.
Everything worked flawlessly: late evening snack upon the first late night arrival, excellent breakfasts and three-course dinners in half-board, private shuttling to Grosté skilift station and center of Madonna di Campiglio and back to hotel, the spacious well-functioning and clean room with nice view, the spa with three different saunas (though as Finns we only used the Finnish, "real" sauna) and a pool, the ski room, everything.
Well done, thanks, see you again! T.U.