The Olympus 50mm macro is a 4/3 lens that proved remarkably good (see the Robin Wong comments on almost technically perfect) with several reviewers using it as a standard lens for testing new bodies.
Olympus have gone head to head with Leica with microscopes and similar equipent and in the past invested heavily in professional macro lens heads and other close up equipment, such as bellows etc.
This review will give a users view and show why the lens you have is in no meaningful way inferior and in some important ways, better. I have never bothered with getting macro lenses for my Nikon or other bodies as the Olympus set up was perfect for my needs.
http://robinwong.blogspot.ca/2012/09/olympus-mzuiko-60mm-f28-macro-lens.html
The 50mm has a 4/3 mount and therefore needs an Olympus MMF-2 or similar adaptor to fit mft cameras such as the EM1.
Unlike the similar f3.5 35mm 4/3 macro or your 60mm, it will not go down to a true 1:1 ratio without an Olympus EX-25 extension tube. The good news is with all this tube and mount it still talks to the camera. For most use such as fungi the 1:1 is only necessary if you are getting very close up and personal with the gills. Your 60mm will go to 1:1 as you know.
Optically it is an excellent lens both for macro use and for portraits etc, being crisp and low on abberations. The f:2 aperture is an obvious help for critical focussing.
The however is that is not a fast a/f lens and has no focus limiter. It will a/f without the extension tube quite happily on my EP-1 and therefore should be even better on an OMD. There is little point in trying to a/f with the ext tube on the EP-1 - never tried it on my OMDs, however at these ranges I manually focus and move the camera for critical focus etc., so it isn't a problem to me. The EP-1 has a multi-angle VF-2 viewfinder which I find useful hence the choice of this older camera.
As between it and the f3.5 35mm macro I already own (that focusses faster and I use for small mammals and reptiles), I don't really need the 60mm as it really duplicates what I've got especially as I have a Sigma 105 mm macro for insects.
If I was new to Olympus I would buy the 60mm you have and leave it at that.
I use the Olympus 9-18mm as my mft wide angle, the Panasonic equivalent is reputeably excellent but I have never tried it and it costs more. The Panasonic 8mm is a fisheye so is probably of little interest.
If you have less need for the more extreme wides there are a lot of lenses that go out to 12mm, including zooms and primes.
I hope this provides some background - all focal lengths quoted are true figures and not 35mm equivalents
Excellent light today for crisp close ups.