http://chriseppstein.github.com/blog/2010/02/08/haml-sucks-f...
As a result, though I love Haml, I think ERb is a more sensible default.
For the few cases where that makes sense, ERb is great. But I have a hard time imagining it's common enough to make it the default.
Edit: Also, the post you linked to outlines several simple ways to mix text into your HAML (inlining HTML, using markdown filters, etc)
http://chriseppstein.github.com/blog/2010/02/08/haml-sucks-f...
As a result, though I love Haml, I think ERb is a more sensible default.