Sorry everyone! Turns out showdowns were down for a good part of the afternoon. We eventually figured out the root of the problem was an issue with our AWS server, however Amazon didn't let us know until about 10 hours after we started having problems.... grrr...
Interestingly, we noticed that our average time on site metric went down quite a bit during this time. Clearly showdowns are a popular feature and we will continue to improve them.
Feel free to comment with any suggestions on how you would like us to improve showdowns.