After about twenty games I have come to the conclusion that the sliders are for the most part, noticeably unnoticeable. Here are a few examples.

All penalties at 100... seven penalties the entire game (versus four I just had with default sliders)
Threshold at zero (on very slow). No major changes in speed differences between players
Hum QB acc. set to 25... last game 16-21 211 yards and 1 td

I'm still 100% committed to getting this game but sliders don't appear as though they will add a lot to the game this year IMO. I really want to see sliders on steroids to demonstrate differences but EA/Tiburon doesn't take the same approach as I would like.