The rooms are very spacious and pleasant. Service was occasionally weak (eg pool bar), but other times excellent (eg room service). There were small maintenance issues like the outdoor shower drain left you standing in water....small things...it isn't a new hotel. The pool is wonderful, a huge 3 tiered square, with plenty of space for everyone. The food was good but not remarkable. The spa is nice and there is also a large indoor heated pool and a decent gym. There are tennis courts, a golf course and horses are available.
It is located in a pine and eucalyptus forest that is very fragrant, nice unless you are allergic to it. The river shore is accessible but not a place you want to swim.
Access to the hotel is via a fast ferry, only 1 hour from Buenos Aires to Colonia, Uruguay and then a 1 hour drive (they meet you at the boat if you like). So it is a nice 2 or 3 night break from Buenos Aires busy streets. Relative to Argentina, prices in Uruguay is expensive and the Four Seasons is no exception.