I would think that despite the new "enhancements", a Gold will still stand an excellent chance of being upgraded to the Executive Floor (the top two floors), assuming the hotel isn't booked solid. At least that was my experience 3 years ago, when I was a Gold. The Hilton tends to treat VIPs rather well in my experience.

Also, I wouldn't recommend Cabana Las Lilas. Do a search on the Argentina forum. The general consensus is that it's over-priced and the food is mediocre. I'll second El Mirasol in Puerto Madero though. There's also a Freddo (gelato) within walking distance of the Hilton. Mmm...can't wait for my trip in December!