Have many of you got got an OM-D that have an E-5 as well and are you happy with it,
Have both, love both, use both.
My $0.02 is - if you are asking yourself the question - don't get it. When the OM-D was first announced I just knew I want it the second I saw it, was probably the first to order it or almost (ordered on Amazono at 12 zero something AM the night it became available for preorder), and never regretted it for a second.
Side to side - the E-5's viewfinder will simply make the EM-5's viewfinder cry bitter tears, if you swap from one to the other. If you forget the E-5 for a second and use the EM-5 extensively - you'll be ok, but get both to a very bright place (say - on the beach), and you will see how good the E-5's viewfinder really is.
Try focusing on a plane with your EM-5 + 75-300mm combo, and you will remember all the "bzzzttt-bzzzt-bzzzt" days of your E-620 + 70-300mm struggle. Switch from that to the E-5 + 50-200mm + EC-14, and you will be in pure heaven.
Then, get both in the city, and try to get that discreet shot of that funny situation with your E-5 + 50-200mm + EC-14 combo. Once you're done explaining to the cops why you were taking pictures of this or that with your huge camera - get the EM-5 + 75-300mm combo, put it at your waist or belly level and just start take pictures by touching your screen.
Long story short - you need both. But if you need to take any action zoom shots, dont expect to get the performance of an E-5 + 50-200mm SWD lens, even with native m43 zoom lenses. Think more like "E-620 + 70-300mm, a bit faster".
Your back into "really fast" territory with the 12-50mm, but it's a different story picture quality wise (although it's a very, very nice lens which I love a lot).