On my initial walkthrough of HentaiKey, I focused on the meat of the homepage. The amount of content is a little confusing at first, because it seems like everything is within sections within more sections, so it does take a few clicks to actually get to the stuff. Having said that, there is a ton of content available in both the original and licensed sub-sections.
There is an original content section, a liscensed content section and then access to GT sites which make up about 500 more. Like I said, it is all a little overwhelming and it does make it pretty impossible to come up with exact content numbers. However, if we say over 450 photo sets and over 20,000 movies (including flash animations and games) you would probably not be that far off.
There is almost too much content available, and it will take one very dedicated member to actually check it all out. Is that member you? Considering all the content you get and the quality of the main and bonus movies, Hentai Key is an easy recommendation to make even with that annoying DRM protection.