wow, another post basically singing the same song, but this time to a slightly different tune....
Whether your a pro, semi pro, hobbyist, enthusiast or novice - to buy, what to buy, or not to buy is all about need vs gain vs intended use.If your a landscape shooter, and have the disposable money/sell enough prints to afford it - go get yourself a d800 and be happy with it. If you make no money with photography at all though, then I have to say it ---you don't have needs at all, nothing is NEEDED, its all wants ---and those people do tend to be the most vocal, and want more than what any provider can offer. Best way to describe this is that they are fickle (because their decisions are based solely on wants which change faster than needs). Not bashing, just making a valid point. If your a pro or semi-pro though, you do have needs. If you work in the studio mostly, and produce images for billboards or other large scale assignments, then yeah, go with the d800. If you shoot a mix of studio/portrait/wedding/event work, then you may find the mk3 to be a very well rounded camera. If you shoot studio/portraits and aren't printing giant sized prints and are using a 5d2, then I can see why the mk3 doesn't offer enough. But if you shoot weddings, the improved AF and ISO do make the mk3 a very worthwhile upgrade. Sports shooters offer a whole different set of needs and wants to the mix - sports shooters need range and for them a better IQ APS-C would be the best fit cause you need the range and may not be able to justify the cost of longer zoom lenses, also, fps and buffer limit are a big factor to you. Needs vs wants though - are you shooting at the super bowl, or your kids little league game? The superbowl shooter has more clearly defined needs, while the little league shooter has wants (and yeah, theres lots of room inbetween, semipros and lower level pros may be earning money shooting, but not enough to afford/justify a 1dx with a 200-400 lens, or any FF camera due to the reach they need - again, the crop sensor isa very valid option for these shooters.
I really think the 7d is a good example of how a 'try to satisfy too many needs in one cheap package camera' shows its limitations. It has this good enough in all categories feel to it, but nothing outstandingly stellar in any one field problem. I would love to see the 7d line re-envisioned, and split into 2 - a 7d2 and a 7dx... one being optimized for low light and IQ, 22 mpx sesnor, lower fps expanded ISO range (a good entry level wedding cam/a really good backup body), and one for sports shooters optimized for fps. I highly doubt this will happen, but one can dream. AS a 7d shooter who shoots weddings, portraits, events and art - greater ISO range and and better IQ at 3200-6400 is far more important than fps. This is also why the mk3 makes sense for me, and once I can afford one I am snagging one (about $800 off now, uggg...I would have one now but opted to invest in lighting)...
As to the mk3 being $500 more than the d800, it really doesn't matter to me. I see the benefits of the AF and ISO range that the mk3 would give me. The d800 would suit the needs of my portrait work, and my fine art work, but not the needs of my wedding and event work - in that regard the lack of sRAW and mRAW options are deal breakers. And as to portrait work - investing in lighting has already lead my clients saying WOW, and thats with a 7D - so again, the d800 ain't attractive enough to do any switching. It all boil down to needs vs wants vs ROI (ROI will only matter to pros and semi-pros).