Q:

What would be some reasons to decide against HAML/SASS?

I've been reading up about HAML/SASS lately and I'm not quite sure why any one would not want to use it.  It seems to be very easy to switch, makes things cleaner and more efficient.

Update:
What about using one or the other?  Most of the complaints (the few complaints there are) I hear seem to be about HAML, would there be any problems mixing and matching XHTML/HAML and CSS/SASS?

Update:
Sorry, one final update to the question.  It seems to me that switching back from SASS to CSS is painless and simple.  What about switching back from HAML to HTML?

A:

If you're using Rails, yes. Go for it. Some issues you will hit, though, will be that any other developer brought onto the team later will have to learn it, as well. If you're already working with a big Rails crowd, that's fine, but HAML/SASS may confuse a designer who's worked with pure HTML/CSS for years.
If you're not using Rails, though, a good HAML/SASS integrated system is hard to come by. There are a few out there, but I imagine they're not as well-supported or as far along with the spec.
But, yeah. HAML/SASS is definitely worth it. The only real issue you'll hit is that it's not yet standard.
As for mix-n-match, HAML and SASS are so similar in style that I'd say go for both, but it, again, comes down to personal preference. Try using both for a day, and if you don't like one of them, switch back. There's no technological issue about it, so do what you prefer.

A:

There are lots of tools for working with HTML and CSS.  The syntax isn't pretty, but the improvements from HAML and SASS don't seem that dramatic to me, and for many they're not worth the trouble. Of course, for those developing web application with widely differing frameworks (differing from Rails that is) it's even harder to find a reason to go to the pain of integrating something so foreign. (Example: care to explain what I'd have to do to integrate SASS into my Java/Stripes/JSP environment? :-)

A:

I've been on volunteer projects where HAML's syntax curve (syntactical whitespace, the automatic generation of tags etc) has been seen as a barrier: one more thing for a programmer new to the project to learn.
Personally, I think SASS is worth it, but I'm up in the air about HAML: having debugged HAML templates before it seems like the typing you don't have to do with HAML is overcome by the time you spend debugging why there's an error on your templates. This could be a (HAML) newbie's perspective though.

