yeah, Helmet rule is the worst thing added so far, though I haven't seen this new onside kick bullshit.
Helmets come off often, and the rule is, unless the helmet comes off as a Foul (which, depends on the ref seeing and calling!), you have to stop what your doing during the play. You can't keep running if you have the ball, or need to tackle someone. If you do move/do something without a helmet, a penalty will be called on you.
Oh, and having to sit out a play.
Games will slow down by a couple minutes just off this rule.