In reply to Francisco.

I feel actually the same.
BEM was dried to use for Frontend. ATM we trying to use it as backend modules and it's great! Methodology is now so good for backend as it can be but still it's great.
And I said it again — BEM is OOM.
Btw we still using preprocessor for CSS with BEM. We writing stylus files for blocks instead of pure css, but it's possible to use anything else like sass, less, or anything else.