I am probably the only tourist in the world with the following opinion: I believe Machu Pichu is overrated.

Before going there, I went to:
Saqsayhuaman (pronounced more or less sexywoman). 30 minute walk from the city square of Cusco. It has much more fine rock work and the rocks are larger. By comparison, Machu Pichu has almost no rock wall worth looking at.

Pisaq - this is a site VERY similar to Machu Pichu, but, is a $1 to $2 public 1 hour bus ride from Cusco, then a $10-$20 cab ride to get to the site, or a very strenuous walk. I walked down. The "city" of Machu Pichu is larger, but the overall site and terracing as Pisaq is much larger.

At $400 for Machu Pichu - I think the Peru tourism industry is simply gouging the foreign toursists.

You can check out my pics at:
http://picasaweb.google.com/ronald.sercely

Just my thoughts.