Treemaps are awesome
Sadly, I mostly dislike tree maps.  At large, I never actually see the tree structure that they are supposedly helping me see.  Well done ones can be pretty, but that is true of basically every visualization.<p>The worst is when someone shows a tree map like viewing of something like a CPU, but that is not at all how those are necessarily logically connected.  Such that many go for an odd mix of tree and heat maps, but then fail to actually show anything useful that a simple ordered list couldn't also show.