I shot with the Lumix S 85 1.8 for a few hours trying to help out a 'wedding photographer' that was a bit in over his head taking on a 16 hour shooting day with rented and borrowed gear. It seems to be an almost faultless lens, especially at that price. It is quiet and fast and the rendering fits in with the real Leica lenses quite well. The Leica 50 1.4 is pretty much the perfect wedding lens to me, I can and have shot almost a whole wedding with that on an SL body. The only drawback of the 50 is how big it is, it actually does scare people a bit. The 85 1.8 does much better in that regard and is much more compact and blends in a little. I wouldn't feel left wanting for anything more with the Panasonic. The 85 renders nice and smooth, quite close to the 50 1.4, which is far more important to me than super shallow depth of field. I like the subject to be isolated slightly, but still have the surroundings recognisable.
I can't speak to how reliable it is on an SL body, but it should be good given how close the companies work together.
Of course there is the ubiquitous Sigma 85 1.4 Art as well, but it is bigger and quite a bit more money.