I'm just not buying it. Look at his example erb code, compared to haml. Which would you rather be typing day in and day out?

In terms of learnability, it takes 15 minutes to learn 95% of the haml featureset. So you spend 15 minutes, then presto, less repetitive stress injuries from hitting the shift key all the time when creating view templates. AND it's much easier to read, and it forces correct indentation. That's just a whole lot of win.

Also, haml and sass are not mutually exclusive, nor are they a pair. They are 2 different tools that work with 2 different things.