I went there today for the third time, and finally was able to see the Temple of the Feathered Serpent. You have to go through Gate 1, instead of 4 or 5 that lead you to the Pyramid of the Moon or the Pyramid of the Sun. There aren’t as many tourists as there were at the other pyramids, which is a good thing. I climbed up a fairly well-maintained set of stairs to the platform, which was a pyramid build in front and on top the Feathered Serpent. The newer pyramid thus shielded the lower portion of old one from damage throughout the past 1,500 years or so.  The platform itself has solid rails and was quite safe.

As to the sculptures, they are spectacular and give the whole site another dimension. I would recommend a visit to the Anthropological in Mexico City to see the fully colored replicas before going to the site to truly appreciate it.