The OM-D E-M5 is selling as a kit with the weather-sealed 12-50mm zoom. I bought one a while ago and reviewed it here:- http://soundimageplus.blogspot.co.uk/search/label/Olympus%2012-50mm%20zoom%20lens%20review
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It would have been nice if the new Olympus had a quality, fast lens to go with it, and the fact that the 12-50mm is the only Olympus zoom to feature weather-sealing to match the OM-D body is also somewhat of a disappointment. Its a decent lens but if you don't require your gear to work in a downpour, I'd be inclined to recommend the 14-42mm zoom as a cheaper, smaller and lighter option. Of course if you can afford the primes then they are the preferred option. They are certainly mine and they given me excellent results whenever I've used them.