The main issues for me with the 5DMKIII are the fact it feels its age now compared to newer cameras. The speed of operation, the viewfinder II etc compared to my 7DMKII it does feel old and they are the little features that make the day to day use of the camera more enjoyable when you use it everyday.
The other things are the banding and colour noise from the 5DMKIII which arent apparent in the newer sensors or to a lesser extent the current 6D.
I had my 5DMKIII for 4-5 years and unfortunately it was stolen. Loved every minute with it and got some incredible imagery. It also went through some abuse - it was dropped in a river, been in yellow weather warning shooting motorsport (and actually gave up after about 8 hours, wrapped it up in a towel and it booted back up the next morning) so many weddings I cant recall, round the world, desserts, tropical rainforests, went through 3 shutters etc etc never missed a beat apart from that one time above. So basically it got well used and abused and never kicked up a fuss. Trim was warn, paint was very warn, and the mode dial was missing its selector dial.
Sorely missed but onto what next...
Cant decide what to buy. I dont need 50mp of the DSr or the editing headaches it brings. The 5DMKIV runs around £3349, £1349 more than a new 5DMKIII at £1999 and a well loved preowned 5DMKIII (30k actuation) is around £1400 £6-700 cheaper again.
Although the 5DMKIV has all the features above making the day to day operation more enjoyable and the technology advancements that the 5DMKIII lacks and more with higher resolution and better DR the differences are not worth 75% more at the moment. The banding and colour noise can also be avoided with good technique, bracketing and post processing.
When the 6DMKII comes out it will undoubtedly replace the MKIII like the 6D replaced the 5DMKII. But there will be some features that the 5D crowd will be used to that wont be in the 6DMKII which will make buying difficult.
Its a tough one. There isnt really a great option currently and im leaning closer and closer to just buying a well loved 5DMKIII. Financially its not a big deal its just more value for money the 5DMKIV is a stellar camera but the 5DMKIII does 95% the same and just think that there may be a fairly hefty price reduction soon making it much more attractive.
Other camera makers directions are intriguing too if I wasnt so invested in canon I would certainly give some other options a go. I love canons aftercare nothing competes with it and the glass is gorgeous, I just wish they would push the boundary a little more. Dont get me wrong the 5DMKIV is great but I cant help but feel it could have been better, although 5 years later it feels like Canon is being blase with the user base that everyone with a MKIII will just jump on board. I have nothing to back up my thoughts but I dont know if this is the case. Many of my fellow local wedding photographers haven't seen the benefit of upgrading other than to replace warn out cameras rather than lusting after them.
When I bought the 5DMKIII I was confident it would last me 5 years but I cant honestly say the same for the IV. There is a lot of innovation and change of direction in the market which could see canons 5 year upgrade timescale into flux.
The A9 for example is probably going to be more a prosumer camera than a pro camera but what they are doing is very interesting.
Time will tell. Canon will do its own thing regardless of what anyone else is doing which has its benefits but also its drawbacks.
Im documenting a 4000 mile road trip for Porsche post on the 18th of June so need to make a decision fairly quickly so that means I cant wait to see what the 6DMKII does to the market. We may see even better deals on 5DMKIIIs new and pre owned and the 6DMKII may bring the 5DMKIV price down by £4-500 like the MKIII did in October 2013 18 months after it was released.
One thing is interesting that not one person has thought that the 6D could be the test ground for a new hybrid mirrorless in a DSLR body that has been rumored. That could be interesting, a 5DMKIII esk camera with some newer technology.
That could be a camera I would be intrigued to play with although I call myself 'an old school shooter' im ready to try some new tech.