The back controls have been moved around a little for more streamlined operation. These include a 7D-like button/switch for Live View and movie capture and the addition of a touch pad to the control dial for silent adjustments during movie shooting. The viewfinder now offers 100 percent coverage, and the camera incorporates the same 3.2-inch LCD that Canon's using in all its current high-end dSLRs.
Not only is it great that the camera has both CF (UDMA 7) and SDXC card slots, but it adds a nice twist to the more common myriad options for them: you can also configure to save say, large raw files to one and small to the other, or differently compressed JPEGs to each.
The 5DM3 uses the same menu and control-configuration system as the 1D X, which in turn copies some of the 7D. I've always found this screen for configuring the various controls extremely well designed.
The status LCD is the same, although it has a few more readouts to accommodate some of the new features, like silent burst shooting. There's also a tiny new programmable button on top. The other controls--metering, white balance, AF mode, drive mode, ISO, and flash compensation, as well as AF lock, AD lock, and focus-area selection--remain unchanged.
While both the camera and the optional vertical grip use the same batteries as the 5DM2, the grip has been slightly redesigned to add a jog controller for improved vertical handling. There's also a duplicate of the manual function button by the shutter.
The 580EXII is getting replaced by the Speedlite 600EX-RT, Canon's first flash with built-in wireless master capability (it supports RF or line-of-sight for backward compatibility). It supports up to five groups flashes in up to 16 channels, plus Canon claims it's got a 20 percent faster recycle time.
Unlike the slim GPS module that the company announced with the 1D X, the 5DM3 is joined by a big hot-shoe model. It does have GPS logging capability, though, which allows you to track your movements between EXIF data location snapshots.