I’ve always reasoned that Haml went against the principles of an MVC framework because the designers would not (typically) be able to work with views written in Haml. I’ve recently come to the conclusion that, in practice, Haml is better for your project.
When I took a step back to analyze what impact a switch to Haml would have on our team I realized something interesting. After we receive HTML from our designers, we break it up into partials, attach unobtrusive javascript methods and make other various tweaks that require the designer to pair with a developer. The notion of keeping the responsibility of view maintenance with the designers was just proven incorrect in practice.
The succinct syntax and close connection to your stylesheets give your developers a more efficient environment. Isn’t this what we’re all after?
Speed concerns? With version 2.0, Haml is now slight faster than Erb and with that goes my last excuse for not switching.
Haml, I will now get to know you better.

I made the switch a couple months ago. HAML takes a little getting used to, but it’s just plain awesome to work with.
Switched a couple of weeks ago to – now I am shivering whenever I see erb again ;-) Yeah, after 2 years with erb, haml was weird for the first few hours for sure, but now it’s just as plain clear as the green chars of the matrix for Neo ;-)