Even if playing certain hands is breakeven (which by ice's numbers they're not, they're plus-EV), playing marginal hands will get you more action on your big hands.

Super-tight is not the way to go in NL. As I've moved up through the levels I always see the super-tight people playing, and they're still at the same level now that they were 5-6 months ago.

Super-tight is great when you're first starting out in NL, but to really max your win rate you need to incorporate some marginal hands (played aggressively) into your game.