Goose

If you don't mind manual focus then the SLR Magics and Voigtlanders are nice.
I picked up a 12mm 1.6t SLR Magic and a Voitlander 25mm 0.95 secondhand and they seem to fit and compliment the philosophy of m43. They are small but solid.
I have come from Canon and I wanted a system that weighs less and takes up less room.

Mine arrived yesterday, body only, so any lens advice would be more than welcomed.... I know, Iknow, I should have asked more questions.

You can use the 17-55mm f2.8 with a speedbooster if you remove the plastic baffle on the back of the lens, which sticks into the mount and will hit the front element in the speedbooster. If you do a bit of googling you will find more info on this.
I would recommend getting a .71x booster over the XL .64x version. Less danger of vignetting and more future-proof, as the GH5 uses the whole sensor width for all video modes.
Canon 17-55 f2.8 vs. Sigma 18-35 f1.8 is something you have to decide for yourself. If you need IS or the larger range, the Canon is your choice, but you will need a proper Metabones booster, as that has electronics to power the lens for aperture control and IS. If speed is your primary concern go for the Sigma. If you get a Nikon mount Sigma you can use a "dumb" booster and that saves some money.
Don't waste your money on any generic booster other than a Mitakon/Zhongyi Lens Turbo II. The cheaper ones have awful flare problems, or are soft.

If you just want to use your Canon lenses, there is also a Kipon adapter that is not a focal reducer/speedbooster and it is  bit cheaper.    
I don't know how well it would work with your camera but it is fine with my GX7 and all my Canon lenses except an ancient film era EF 28-90.      Doesn't work for AFC with my camera but AFS is pretty quick and fairly accurate (and including my EF-S 18-55 IS ii kit lens).       It doesn't allow IBIS with my GX7 and Canon lenses for some reason but IBIS is fairly limited anyway with the GX7.    IS works well when that is in the lens.
IF AF in video or AFC is required, native is still better (except for the Panasonic 20mm 1.7 at least).
If you can afford it, I would recommend at least trying a AF adapter/speedbooster to use your lenses especially if keeping dual systems.

"6K/24p Anamorphic Video Mode, while fun, is severely hampered by its 4:3 aspect ratio"
UM!
That's what an anamorphic mode is - 4:3
Someone let our dear friends at Cinema5D know.

Nice hair tones...

Eventhough the gx80 is a great camera, especially if you take the price into consideration but if you had to make a choice then the G80 is a better camera allround and worth the extra investment, the internal audio on the gx80 is really bad, you can't plug in a microphone, the viewfinder is too small, the lcd screen doesn't flip open and it doesn't have cine-d or v profile. These are all shortcomings the G80 does not have, for me the G80 is camera of the year.

Albert ( @Brother ) traded in the G7 for the GX80! Of course he had to go and get one of the sickest lenses out there for it.
 
 

Damn! There was always a chance that this little thing could get lost in all the 4.6K hype, but no chance...amazing image!
I want one.....

Un-foogin-believable.

The rendering of the smoke was like nothing I've seen before - looked like it was going to come right out of my screen.

This 8k thing is a whole new world for Documentaries, educational, and other types of super-realism stuff.

But I'm becoming more convinced than ever that 4k is the cutoff for "Movies". It's just too sharp and it starts hurting the feel of the experience instead of helping.
In fact the 2.8k Alexa or even the 2.5k Blackmagic Cinema Camera are about all I'd want to deal with if the intention is something that "looks like a movie".

But it's interesting - we now have cameras so advanced that they are creating new genres. That's fantastic.
And the ability of 5k, 6k, and 8k to convey a realistic experience is a gift to Humanity. As a teaching and world-sharing tool there has never been anything like it before. 

There is very much a parallel in Music recording. - Audio technology has advanced just like video technology has, but when the audio you want to make is MUSIC then the new advanced tech sounds 'worse' and everybody reaches for "tube this" and "tube that" and "tube emulators"... all that DEGRADES the audio - but it does it in a very specific way that just so happens to sound "better" to most people in the context of songs. 
So "movie" cameras will be the ones that render a technically less advanced image - but one that is far more suited to the particular application of creating a "movie".

Interesting times.

Looks beautiful... Colour, contrast, detail, DR and general IQ all have a touch of magic. Really like it.
The IMAX shooters are gonna love it!

Unfortunately not quite D5300 / GH3 good. Canon's new APS-C sensor doesn't have the moire & aliasing control of the former or the resolution / sharpness of the latter.
D5500 even better as it has the lovely flat profile and newer sensor, very very clean in the shadows.
Canon continue to disappoint - the 80D is basically a non-event, when it could have been a game changer.

Whoa !!! What's wrong with Everyone on EOSHD???
Andrew didn't say a super 35mm sensor. Only a 35mm size crop (with a M4/3) lens setup. Sensor will be the 1.86 crop like on the GH2, not the smaller 2.0 Crop like on the GH4. 
There could be a Panasonic built-in equivalent of the Metabones lens booster. Whatever is needed basically for a wider frame.
 

Would rather the focus be in dynamic range, super 35 sensor, color and 10bit or raw output than 6k.  

Bigger sensor size is good and all. But I would like more DR, better highlight roll off, less noise and improved color science even if only at 1080p in a better codec.
 
 

Good honest review Andrew - thanks.  looking forward to part 2.  Interested to know if the heat issue could be mitigated by swapping batteries or using an external power source.  

Finally a high megapixel dslr from Canon, great solution for those who can't afford Hasselblad, Phase one etc. for video:  there are enough different options.

​No improvement in DR after 7 years in unforgivable...for a stills camera. 

Someone really needs to sit people down and explain that a DSLR is not a video camera. Apparently a lot of people still don't seem to understand that.
You don't complain about video cameras taking crappy stills, why do you continue to complain about stills cameras taking poor video?