I visited the Taj with a group of friends and our friend from Delhi. The Taj is something that was on each of our bucket lists, and I can say that it fell completely short of any expectations. Here's why:
Getting There:
-It is a brutal drive from Delhi because of city traffic. There is little to do in Agra, which is a very poor, dirty city located near the Taj.
-When you arrive on grounds, tuk tuk and camel drivers will swarm you to have them take you from the parking lot to the entrance gate (~200 meters).
-You will also be solicited by street vendors and children trying to steal your bags or beg for money. MIND YOUR BELONGINGS.

At the Taj:
-You will take some beautiful photographs -- Photographs you could have seen in a magazine rather than endure +100 degree temperatures and hoards of people for.
-There are no restrooms.
-All you can do is walk the grounds, walk inside the mausoleum, and walk into the mosques on either side of the main building. Let me emphasize: ALL you can do is WALK AROUND.
-The buildings are beautiful, and the stories and legends behind it make it enchanting, but the actual visit itself is lackluster.
-As a foreigner, we as both in a group and individually were approached by dozens of Indian families and for pictures. In the two hours we spent there, we hard our pictures taken by +20 Indians/families.

Other Details:
-As a small aside, unlike other historic monuments, the Taj does not have anything to describe what you are seeing (i.e. tours, brochures, plaques). There are literally only the grounds, and nothing else, so read up before you visit.
-Bring water with you. There is nothing sold on the grounds, so you will regret not having something to drink with you before venturing out.

Though Beautiful World Heritage site and an architectural wonder, less is done on making it a International Tourist attraction.