OM-D E-M5 and Olympus M ZUIKO 14-150mm f4-5.6

If you get a sharp copy, it's a good lens, but extreme edges are a bit soft on all copies.  It's a good performer in good light.  For less-good light, you should switch to something faster, like primes.

As a daytime vacation lens it works very well.  The fast autofocus shouldn't be dismissed.  Odds are you're using a lens like this because you can't take the time to switch between more than one lens.  That probably means you're wandering around somewhere with friends or family.  Fast a/f allows you to get more shots, and accurate focus ALWAYS trumps lens sharpness!

If you're doing more contemplative photography, primes will give better ultimate results.