We're finishing our third night here and it's interesting to compare and contrast our impressions to those of two years ago when we first stayed here.
The same friendly Aussie concierge, Victor, is still presiding in the lobby and even pretended to remember us.
We checked in at the 8th-floor lounge desk and got our room promptly, despite having arrived at the hotel from our UA flight into EZE around noon.
We found out the 8th-floor lounge is currently being renovated - lots of horrible grinding noises and vibrations that may be tile removal but the noise isn't loud enough to bother us in our nearby 8th-floor room - and the "presidential suite" on the 9th floor is being used as a substitute. It's not a bad venue and includes a huge balcony that must hold ten or more tables. No plaque on the door saying "El Presidente Bill Clinton slept here" though.
We noticed and rectified a few little details after we arrived. They failed to provide us with the welcome letter until we asked (we like to see spelled out in writing the hours for breakfast, etc., and to what amenities we're entitled), there were no bathrobes in our room (brought promptly on request), and they failed to replenish our water yesterday.
We also had our conditioning unit suddenly start to drip a stream of water through a pot-light in the entrance way and maintenance was up quickly to fix it and the minor mess was cleaned up as well (we probably scared them since we first suggested it might an overflowing bathtub upstairs).
The lounge staff are perfectly friendly but there seemed to be so many different employees at that 8th-floor lounge reception desk not far from our room that we didn't really establish much in the way of casual human contact with any individuals. Maybe we're getting fussier, but I'd agree the breakfast buffet is no great shakes, even though there's a fair amount of variety: scrambled eggs, bacon, little sausages, and pancakes at one end, along with a selection of fresh fruit, yogurt and varied bread and pastries, all nicely presented.
The evening appetizers are also "okay" at best but not spectacular, leaning to the starchy. The alcohol includes several wines, beer, and a reasonable variety of hard liquor IMHO.
Edited to add: Tonight there was only one red wine, a fairly thin cabernet, a white, and a sparkling. We also noted the number of plates at other tables with uneaten hunks of bread left on them. There's very little food there that's not attached to a piece of bread and the one warm item was some kind of empanada more reminiscent of a British pasty. I'll now say definitively that the food and service have deteriorated seriously in the lounge since our previous visit, with one young employee only to have us sign those annoying sheets confirming our room number, busing tables, bringing out additional food and wine, and presumably plating food in the back room.
We happen to like the Puerto Madero area but understand that it wouldn't be to everyone's taste. We're moving to the Marriott tomorrow as there was no room availability here - maybe an influx of people on the cruise we're leaving on or another one. It'll be interesting to compare the two as we bought lounge access (being lowly Silvers) at the Marriott.
Finally, there are two 220 outlets next to the desk I'm sitting at; one fits a standard American plug and the other has the two prongs set at angles, i.e. like an Australian plug.
There was allegedly 15% inflation in Argentina in 2009 alone with 20% predicted for 2010, so maybe Hilton is cutting back here and there or maybe we're turning into a couple of jaded hard-to-please old crocks.

We still like the property, we'd still return, but I think the temporary lounge arrangements, coupled with what is a decline in the breakfast and evening appetizers, are preventing its being the "Wow" experience it was two years ago.
OTOH it's my first and probably last time to see the inside of a presidential suite.
Cheers,
Fredd