James Britt wrote the definitive post (in my opinion) on the use of Haml: http://www.jamesbritt.com/2009/4/29/thoughts-on-haml
Thanks for the compliment, though the idea of "definitive" anything typically makes me bristle. . I stand by what I wrote, but I wrote it mostly because enough people kept asking me why I didn't care for Haml, and I'm sort of bad at keeping my mouth shut.
As a happy Python user, I absolutely resent going to languages that require code block delimiters. Since I consistently indent anyway (and have done so since long before I ever discovered Python), it just feels like pointless duplication of effort to indent and delimit using curly braces or do ... end or whatever.
Significant whitespace may not be for everyone, but there's no case to be made that it's punitive.
There's a worthwhile difference between Haml's "must be this distance, exactly" approach and the offside rule of Haskell. That I cannot add some extra indentation for clarity or ease of reading in Haml is wrong.
BTW, is there an auto-format plugin for vi that will automatically set/adjust the indentation of Haml if it is misaligned?
As far as know, it's up to the typist to ensure that each item lines up exactly so, which is extra work (i.e. punitive), but perhaps I've just failed to find the right plugin.
Horses for courses.