If you need edge to edge sharpness the 12-50 just isn't the right tool for the job. Luckily there are quite a few excellent options for m4/3 such as the 12mm f2.0, 20 and 25mm's and the 45, all of which are a good bit sharper than it (and even the 14-45, which I own as well)
While the 14-45 is a good lens for a kit zoom, you have to remember than your giving up some features such as the option for electronic zooming, and also a weather sealed build. Not to mention going to a far more useful 24mm equiv on the wide end. Its simply a lens that would be great for general photography at the beach or any other places where you don't want to be changing prime lenses and worried about the elements as much.
Also don't forget that while the 14-45 is a great kit zoom, Panasonic themselves don't even include it anymore, now offering the 14-42 which doesn't compare. I have the 14-45 and got a 14-42 with a G3 I tried and while okay for what is basically a $100 kit zoom, it didn't come close to the 14-45. Probably the very reason the 14-45 still sells for so much when 14-42's are a dime a dozen (not literally)
Personally I applaud Olympus for giving a pretty highly spec'd "kit zoom" like the 12-50 with all its features for just $300 with the EM-5. They could of just thrown in the 14-42 kit as the only option and said spend $500 if you want a weather sealed lens to match your body.