I agree on the haml front. Whilst long-term web developers will appreciate the haiku-like syntax, ERB is significantly easier to parse since it's HTML plus code. To use HAML effectively you ultimately need to learn to "read" a new language.

I strongly recommend any devs, including the Padrino crew, to keep examples/guides in ERB. It's much more friendly for newcomers to the framework. Having to learn to read HAML at the same time is a PITA.