As been said, according to AMCAS an A+ is no better than an A.
That said, I find that grades have a huge psychological factor for me. The less margin of error I have, the more pressure I feel and consequently, the worse I do. If I aim for an A+, the absolute best, then I feel less pressure and have some "fiddle room" in case I don't do well on an exam -- and I still get an A. In the times I've though to myself "I'm only aiming for an A", I slack of where I shouldn't have and end up really pressured to maintain an A. Sometimes I've gotten a B when an A was easily within reach.
So in the end, no, an A+ doesn't mean anything but keeping your eye on the prize might help you pull off at least an A with minimal stress.