Truly excellent hotel on the edge of the Recoleta, one of the better in-town neighborhoods in B.A. (but mere blocks from the few good shops and restaurants). Incredibly friendly, helpful, courteous, kind, unstuffy staff. You really do feel like a welcome guest everytime you walk through the door. Overall, I would say it's the best hotel staff I've encountered anywhere in the world.
The front desk staff was terrific, the breakfast servers were exemplary and the business center staff was incredible. While everyone was fantastic, the concierge desk was the real standout. They could not do a better job for you, try harder to please you, or be more accommodating to your needs.
The newly remodeled rooms are elegant yet contemporary, and the restaurant is beautiful as well, though oddly deserted at dinner time. The lobby bar was usually quite full, and is a nice place for a casual dinner. The pool area is small, but on a warm, humid spring day, it had a great resort feel to it and an excellent staff as well.
The employees are what make this physically top-notch establishment what it is, a world-class hotel in a startlingly faded city. It's the people (and the food) that make you want to come back to B.A., because it's NOT the "Paris of South America" by a long shot. Those glory days are long over and while it is a safe and interesting city to visit, the overall architecture is initially quite depressing (bad 50s era Peronist apartment buildings are everywhere -- unpainted and falling apart).
Almost all the French-style buildings were torn down and replaced by "modern" buildings years ago. Watch where you walk, because it seems all the sidewalks in the city are crumbling and in many places, missing big chunks (except for the Recoleta). The biggest avenue in the world, the Avenida, is surprisingly seedy for the most part and its landscaping is mostly nonexistent. The presidential Casa Rosa is not even rosa all the way around (part of it is an unpainted gray concrete and decayed). The famous Teatro Colon would be beautiful, if it weren't completely delapidated and the home of dozens of homeless people permanently camped out in back. That said, it's an amazingly vibrant city for one that's been so beaten up economically.
We were supposed to stay at the Alvear Palace for a few days as well, but after visiting it, we opted not to. We only saw the lobby, but it has the feel of a semi-remodeled, older Parisian hotel with a surprising amount of tacky tourist things in the lobby. Not bad, but not nearly as luxurious-feeling as the Four Seasons (which is just a few blocks away).
In B.A., I wouldn't stay anywhere but the Four Seasons, but the other hotels that might be worth checking out include the Sofitel near the business district. The lobby and restaurant were great looking and appeared new. A few blocks closer to the river, the Luxury Collection Park Tower, though actually part of the massive and dated Sheraton that's seemingly always full of conventioneers, had quite an elegant, separate lobby and sits closer to downtown as well. (Not that downtown is where a tourist would want to be. The "main" shopping street, the narrow Calle Florida, can be avoided if you dislike pushy crowds and tacky shops).
The hotel in B.A. to beat will likely be the Park Hyatt that opens next year. It will sit between the Four Seasons and the Alvear Palace in an impressive, block long, park-like setting smack dab in the Recoleta.
Until then (and possibly beyond), the Four Seasons is by far the best hotel in B.A., and an excellent outpost of the fabulous Four Seasons chain.

The Four Seasons has a terrific location in Recoleta -- the neighborhood is charming and completely safe for wandering (we walked around even after dark). The rooms are lovely (amazing double-glazed windows that block out all noise and true blackout curtains that allow a great night's sleep with no city light seeping into the room). The fitness center is very well equipped (state of the art cardio machines with individual tv sets and cold towels/water for refreshing after a workout).

The best thing, however, is the concierge staff -- they are truly outstanding and it is worth choosing the hotel for the concierge service alone. Anything is possible in their eyes and they go the extra mile to arrange things (no matter how last-minute the request). The concierges are engaging and friendly and clearly happy to help any and every guest. Their attitude and suggestions make a visit to BA that much better.

We will definitely stay at the Four Seasons again whenever we are next in Buenos Aires.

The hotel was wonderful, clean and the staff was very helpful.

Positives: location, view, bedding, shower, usual Four Seasons stuff...

Negatives: Construction noise despite requesting a room away from remodeling.

We just returned from a 5 night stay at the Four Seasons Buenos Aires and can not speak highly enough about the hotel and staff. And, oh yea Buenos Aires is a wonderful backdrop, more comparable to Paris than South America.
We had three rooms on the 12th floor, two facing the Rio Plata and one the Obleisk. They were all great, remodeled rooms. I must say, the remodeled rooms were nice, much nicer than those that had not been remodeled yet. Be sure to ask for a new room and high level to avoid the nose from July 9th St.
Both Yael and Georgina were wonderful concierges, all the places they recommended were fantastic; Piegari, Cabana Las Lilas, Obrieto?,
and Bar Uriche were all great places. The shopping around the hotel is also top notch. Be sure to check out the art work in the hotel, especially the Mansion. It is a top art collection and they have matching documentation to help the novices- like myself. The rest of the staff was also great, very attentive and very professional. We had a colleague stay at the Faena and he preferred our hotel too.
Wait to go Buenos Aires Four Seasons, you have us hooked on Argentina and we can not wait to return!