A lot of IDEs/text editors can autocomplete HTML closing tags, so I find the comparison based on characters moot.
I'll admit it might make things easier to navigate with the eyes. But on the other hand it seems to abstract something that's really not that complicated to begin with.
A lot of IDEs/text editors can autocomplete HTML closing tags was my initial response to HAML. I was dragged into using HAML, and I'm glad/frustrated for it. Glad, because by the time I finished that project I realized how much faster/easier it made things; frustrated, because the following day I started another (rather large) job in which HAML wasn't an option. It's hard to put into words why I found HAML superior to HTML. A really poor way of explaining it is http://en.wikipedia.org/wiki/I_know_it_when_I_see_it - just replace see with do.
As for SASS, maybe I'll feel the same way after I jump in, but the idea of adding a layer of abstraction to CSS seems like trouble - IE 6/7/8 is trouble enough.
Sass can actually help quite a bit with dealing with the IEs. Compass (http://compass-style.org) has a bunch of mixins that are fully cross-browser and make short work of a lot of compatibility issues.
It is so. much. faster. to write. I've never been able to articulate why, but, in particular, if you do interaction by lighting up DOM elements by class in jQuery, Haml is like having a language designed to lay out UIs.
Iunno, 99% of my HTML writing is copy & pasting. I just write one thing and usually just copy and paste it around. The bottleneck is in fixing CSS and cross-browser display, not really the speed of HTML coding.
That being said, if your HTML development style is based around writing everything then I can see how it would be faster. But for me I use autocomplete+copy&paste, and then usually a lot of other stuff I (embarrassingly) google and then copy from examples.
I started writing an abstraction system... Then I realized about 5%, maybe even less, of my development time is actually in the HTML. Even for front end most of it is in CSS/javascript after you get the HTML structure ready. Copy and pasting is because much of that structure is repeated, but still there isn't much copy and pasting on the whole.
I'll admit it might make things easier to navigate with the eyes. But on the other hand it seems to abstract something that's really not that complicated to begin with.