I just registered to reply because I feel I can contribute something. I've been a member of Fredmiranda/POTN/DPreview for at least 6+ years and have been using Canon digital cameras for 10 years. A 5DII is currently in my bag. I would call myself a near-professional hobbyist
To be honest, I have been disappointed with Canon lately. I get the feeling they offer us the scraps from their table, at a slow pace (for the tech world), and they charge outrageously for this technology. I frankly think they are arrogant and don't listen to their customer base much at all. Whereas, I think Nikon does. Every product of Nkon's since the D700 has outclassed Canon in terms of features. For example, it was Nikon that started pushing dual memory card slots for entry- and mid-level cameras. Nikon has put considerably more pressure on Canon as of late and we Canon users should be thankful for this.
I also think that Sony (Nikon) sensors are superior to that of Canon in two key ways:
1. Analog-digital converter integrated directly into the sensor chip
2. 3D color matrix metering: exposure metering system, operating on data from a dedicated RGB sensor
Every kick sick of Canon's overblown red channel?
Anyway, all this talk about Nikon led me to rent a D600+ AFS 24-70 2.8G combo from LensRentals a few weeks back. Based on the 4-day experience, I came to the following conclusions:
Nikon Pros (D600 vs 5DII):
Dynamic Range
Metering
AF speed & accuracy
Size & Weight
Availability of some nice, new "value" primes like the AFS 85 1.8G that is superior to the Canon
The best UWA zoom in the business: AFS 12-24 2.8G
Nikon Cons:
Menu layout
Comfort in the hand / grip
Overall build quality, fit & finish (Camera bodies and lenses)
Many lenses not as good as Canon's: 24-70 2.8L II, 70-200 2.8L II IS, 85 1.2L II, etc.
In the end, I came away feeling that Nikon listens to its customers, wants more of them, is trying harder than Canon to get them, is making products that offer a better value in many respects, offers a product with a better sensor in terms of dynamic range and RGB metering, BUT (a big but) is trying to do all this at cut-throat speed and margins to the point that quality and customer service is suffering greatly. Whereas Canon charges a premium for products still mainly Made in Japan that represent a better long-term investment and will likely hold their value longer. Canon products are solid and if I were a field photographer, the choice would be easier in Canon's favor.
After my experiment with the D600, I came within a click or two of selling all my Canon equipment and switching, but I held back. I now read lots of dust/oil complaints with the D600 and this reinforces my impression of the camera's overall fit and finish.
My hope now is that either Nikon will come clean and do a recall, will release a "fixed" D600s, or Canon will fix its dynamic range and metering problems with the 5DIV and in the meantime I will continue to invest in good Canon glass.