According to Zap2It, yesterday, the RNC pulled 22.8 million viewers during the 10-11 PM (cable)/10-11:17 PM (broadcast) hour. That's up from the 20.1 million who viewed night 3 (which was really night 2 due to the hurricane) in 2012.
The overnights are missing PBS and CSPAN. Not sure how much they add to the conversation for comparison to previous years, but for those of us not wanting to watch as much spin, CSPAN or an online-live link has been the way to go.
Some cable companies are carrying an in-house RNC feed as well.