A NY Classic
My wife and I were recently at the Pierre celebrating our anniversary. We were married in the ballroom of the Pierre. For this trip, we booked a basic suite, and were automatically upgraded to an 800 s/f executive suite overlooking the city. The hotel claims to have been through a major upgrade but to us it looked pretty much the same as it did many years ago. In some ways, this is probably appropriate. The hotel sits on the corner of 5th Ave and Central Park South abutting some of the most expensive real estate in the country. So all of the wall murals and the Persian style rugs; the elevator attendants in white gloves and the moldings and details along the ceilings... they seem appropriate for an age old classic hotel like the Pierre. So, while the hotel claims it has made updates, it still looks pretty old (and in some places a little ragged), but that was ok with us - it is a grand old NY hotel. The change of ownership to Taj hasn't affected much at all other than maybe the room service menu which features more South Asian flavored fare than in the past.
The service was excellent. Every one will have a different experience, but our's was first rate. From the doormen to the check in to the elevators and concierge, everyone smiled and was helpful. We had a breakfast included in our rate, and when we slept in and missed breakfast, they accommodated us immediately by telling us that they would add a $70 food credit so that we could order room service or have an early lunch in the hotel.
We ate in both restaurants. The tea room was great. The food in both restaurants is now provided by the owner of NY's Le Cirque, and everything was top notch from the smoked salmon dishes, to the cheese selections to the authentic pastas and sauces. 
I went for a run in Central Park, and also worked out in the gym. It is small but there was no one there and had everything I needed. There were complimentary smoothies, fruits, bottled water and newspapers.
Our bedroom had high ceilings and a separate living room overlooking northern Manhattan. The decor was a little dated, but again, probably fitting with the hotel's personality. 
The location is excellent. If you are here for museums, Central Park, Fifth or Madison Ave shopping - this location cannot be beat. 
On the negative side, there were some minor stale odors in the hallways, the carpentry, wall painting etc on the upper floors looked a little old or sloppy; but none of this was a real drawback. 
Obviously The Pierre holds some nostalgic value for me, but apart from that it is simply a classic NYC hotel, with full service in every way, excellent food and a stellar experience. And in terms of value, while our room was expensive,, all in all, it was only about $200 more per night than many other newer hotels with closets for rooms. Our room was gigantic by NY standards and I think it actually represented good value.