My wife and I recently went to Posh and had the full tasting. We had reservations and were seated as soon as we arrived. Our waiter was helpful explaining the menu and the "improvisational" concept.
The courses were small, but when you're getting 10-12 "tastes" the portions were just right. Overall the food was OK, but not what I would consider spectacular. The experience was unique for sure, but the cost of the meal (~$500 w/tip and one wine pairing for my wife) was expensive.
The service could have been better for such a high end restaurant. We were served by a number of different people throughout the meal so it was hard to tell who was in charge of our service. We also did not receive new silverware with each course, which was not a big issue, but it would have been nice not having to lick my silverware clean after each selection.