I'm deep in Sonys and Canons but added the m4/3s for size/weight considerations. In a pack weighing as much as my 7Dii and 400DOii I can have the Gx7 or GH4 and 5 lenses. When I grab that pack I'm giving up BIFs kinda, because I've done some BIF work with the GH4--just not as easy as the 7Dii. I'm def. giving up low light performance sensor size wise but you know that going in-in return we get the DOF bonus from that sensor. My hope is that the OM-D M1 mark II when it gets here has made big strives in autotracking--that and the Olympus 300 F4. Will that happen? a BIF machine at that size and weight-I can only hope.
Here's another plus. I set up the GH4 yesterday timelapsing hoping to nab some lightening. I went into the basement on a project, soon heard the big rain coming down-me knowing the GH4 was on the dock with only a Walmart plastic bag draped over it. Attached was the 12-35mm Pana lens. Since both are weather sealed I didn't give it a second though. Once the storm was over and my project complete I retrieved the rig. The front element was covered in rain drops....let it air dry and all is good.
If you do get one check out the 4K Photo feature. I've discussed it here at POTN in the digiscoping thread. The GH4 has many tricks up the sleeve.