I have a Panasonic GH3 and Olympus Pen-F, and am using Lightroom 2015.1. Macbook Pro 13" with 2.9ghz i7 processer, fast SSD drive, and 16gigs of RAM.
Issue #1: The GH3 RAW files work fairly well and load reasonably fast (but MUCH slower than they did with my old version of LightRoom 5). However, my Pen-F RAW files load much slower (2-3+ times slower). It takes forever to generate previews and move between photos. I realize they are a bit higher resolution (20MP vs 16MP with the GH3), but it doesn't seem like such a small increase in resolution would create such drastically slower performance. In general Lightroom seems to get more sluggish with each update (I still sometimes use my version of LR5 with my GH3 and its very quick and snappy, unlike any version of LR CC that I have used), but it seems unreasonably slow with my Pen-F files. I have also noticed that Adobe RAW and Bridge seem to work with the files much faster and easier.
Issue #2: The Pen-F files also won't show a 1:1 preview in the import window (which I use all the time with my GH3 imports). When I click to zoom in, it zooms in just slightly, but not enough to really compare sharpness, etc. Is this a bug with Lightroom, or does it have something to do with the RAW files themselves?