For contrast, I went back and read Brendan Gregg's explanation of heatmaps and found the concise explanation of the mechanics clear and easy to understand:

http://www.brendangregg.com/heatmaps.html

TBH, the Honeycomb overview felt long and difficult to get through. Does anyone argue against heatmaps and demand a case be made justifying "why heatmaps"? This read like it was fighting hard in defense heatmaps; against who I'm not sure :)