Most of the time I play on semi-fire. I use full auto when I feel really f*cked/surrounded because it tells people where I am.
I use a stock CA SCAR-CQC w/ a scope. Highest FPS chronoed with it was 348. No idea what it's ROF is but I use a 9.6V too just to give it a little boost.
My view of a high ROF is that it's okay as long as the user doesn't over use it. Anyway if you play a game where there is a max ammunition it's not a long-term problem