Stayed at VAIN in the week of Thanksgiving, primarily because we wanted to stay in Palermo and the other top boutique hotels I was looking at were fully booked. Based on positive reviews from this site, decided to give it a shot, and went for the "Junior A" suite; called the hotel directly to make sure we got a room in the back so we would not hear noise in the middle of the night. The owners have done a great job renovating and converting the building, but the hipness factor definitely does not justify the price they are charging.

The positives:
-Great breakfast; we stayed at a couple of other places in Argentina, and breakfast here was the best
-Friendly staff with good English; we got a good recommendation for La Retirada, a nice restaurant nearby

The negatives:
-While Palermo is an up-and-coming area, the street where the hotel is located is quite run-down and dirty; did not feel safe walking around in the evening; definitely take a cab
-The rooms are small - our "junior suite" was a small-sized room compared to hotels in the US
-The furtniture is cheap and impractical - you don't get a closet; there is a shelf/drawers combo, and you can hang up your clothes on a hanger, but your clothes are in full sight; no door to close
-The AC is non-functional; it was a very old model, located high up on an internal wall, it was loud, and the air wasn't cold at all; as others mentioned before, YOU HAVE NO CONTROL OVER THE TEMPERATURE
-The first night, we found a COCKROACH on the floor
-The bathroom tiles were moldy and did not seem new or clean

This was our first visit to BA, and we definitely want to return, but next time we would stay in Recoleta; Palermo is just too far out of the way and the boutique hotels have a long way to go to live up to their aggressive price tags

My wife and I stayed here during the first week of 2008 and had a great experience. The staff was so helpful with planning a tango show, golfing at the city golf, going to an estancia, and arranging a half day at the spa. The staff sincerely seems glad to help...its not like they are just looking for a tip. The breakfast was delicious everyday and served expertly. The hotel offers free wireless internet. Our room was on the first floor and was just as we expected. Its a very modern room that uses its space very well. We were comfortable the whole time. The shower / toliet area is a little small but it wasn't really bothersome. There is a very modern elevator for traveling to the upper floors. The top floor has a great indoor / outdoor common area. It was very peaceful anytime we stopped up there. Some previous posters seem disappointed in the lack of luxury. I really feel their expectations were misaligned. This is a modern and chic boutique hotel. It has style and charm. The whole area of Palermo is a wonderful place to stay, eat, and sleep. We got to know locals at the laundry, market, and shops. I highly recommend this hotel to someone who likes the boutique experience. The hotel is very fitting with the spirit and vibe of Palermo.

We booked a senior suite for a 6-night stay over the New Year holiday based on a recommendation and the great photos on their site. Only problem was that our senior suite did not have a small balcony as shown on the website or the neat looking indoor/outdoor bathroom. Instead we had a dark room with only 1 window to an interior atrium. As others have noted that means NO privacy if you dare to open your window. Which you definitely need to do because the air conditioning is out of your control (no in room thermostat as others have noted.) Felt totally ripped off. Would not have stayed if we hadn't prepaid.
Look, if you have one of those great upper suites on the top floor (which we THOUGHT we had) you will no doubt find the Vain charming. Otherwise you are in for a lot of noise. The hotel is indeed visually alluring...as you can tell from the website a lot of thought has been put into the design. But it is all Form over Function. The vast majority of rooms are accessed from the main interior courtyard and as mentioned that is also where you have your only window. Yet all the floors are concrete. So you can't help but hear everyone coming and going.
Inside the rooms the form over function principle remains intact....not one hook to hang a wet towel. No counterspace to place toiletries...seems that would ruin the aesthetic of the very hip sink. The first room we were shown (208) has a built-in along the wall that faces the bed--with two open (no door) closets for clothes. So once you unpack you have the lovely experience of staring at your clothes from the bed...Again, what looks great when it is not lived in, becomes icky once you actually try to live in it. We were moved to a quieter and brighter room...but even then we couldn't open the windows and pull the shades unless we were willing to put on a show for everyone using a stairway next to our window.
On the positive side: wonderful staff. Really helpful and lovely. And I saw some earlier comments about housekeeping not being up to par. We found it just the opposite...they were terrific. And the public living room on the top floor is very very nice.
If you book--and are actually given-one of the senior suites on the top floor you will no doubt have a great visit. Otherwise, I would consider looking elsewhere, unless you don't mind a bit of noise ands no air flow given that you will be stuck in a room with only access to a glorified air shaft/atrium. For the money I bet you can do better.

The hotel was very clean and modern. The staff were very friendly, spoke perfect English and were very efficient. Our room, in the 'I' range, was small with a very dark bathroom, containing a shower, toilet and bidet. The wash-basin was actually in the bedroom itself. The only window was the glass door of the room which led into the corridor so we had to keep the blinds closed.

Breakfast was excellent with very healthy options for Argentina.

The location was fantastic. Very close to the subway and on a lovely residential street, within easy walking distance of great shops and restaurants. We loved Palermo.

My thoughts on leaving the hotel was that it was over-priced for what you got and I'm sure there are better-priced options in Palermo.