The Hyatt is indeed a fine hotel, although in the end its just another Hyatt. If one is open to explore new types of experiences, I would strongly suggest trying alternative lodging in a somewhat less than urban setting. I suggest looking into the following places:

Postales del Plata - http://www.postalesdelplata.com

Cavas Wine Lodge - http://www.cavaswinelodge.com/

Lares de Chacras - http://www.laresdechacras.com/

For the budget minded, some options to consider are:

Hotel Aconcagua - http://www.hotelaconcagua.com/english

NH Cordillera - http://www.nhhotelesdirectorio.com