I used to beta for spikesfool for a time. I can't say I caught every grammatical error, but I read the chapters thoroughly, and thought about them, and visualized everything. I never tried to steer the plot, but I pointed out when something seemed out of context or if I couldn't picture an action sequence in my mind. We had a really good partnership while it lasted.

I have to be honest, I don't know the exact definition of meta. (And I don't think I really enjoy it) But in my limited knowledge, it seems like it would lose something if it was beta'ed. It seems like it needs to come unfiltered from the writer.