I'm sure these have been covered to death in other forums or blogs or whatever, but hopefully someone will find some use out of it...
#1 there is no more dedicated question for expandable ISO on or off... The other day I was shooting a pro model to bolster her portfolio and mine, and I was outside, late afternoon, shooting with off-camera flash, with the sync speed stuck at 1/200... I wanted shallow(er) DOF so I really didn't want to go beyond f8 if i could help it. I didn't have any neutral density and I only needed to go down 1 stop from ISO 100... so ISO 50 fit the bill... Every camera with expandable ISO i've ever shot with had a simple yes or no, on or off expandable ISO and viola, all the extra ISO's magically unlock. This camera in the ISO settings allow you to manually select which is the lowest ISO setting you wish to use and what is the highest. For some reason my brain thought that was to do with AUTO iso settings, but that controls expandable ISO's as well. Also to access min shutter speeds for auto ISO, it's in the ISO menu as well.
#2 Talking about menu's, it is totally different... A lot is the same but a lot is different. Same feel as the 7D and 5d2 menu's but a lot of reshuffling, a lot of options bundled together in submenu's and such... take time to get use to it. If you really dont get used to it, it can get weird very quickly.
#3 AF look, feel, and customization is a lot like the 7d. I noticed there are a lot of 5d2 and 1d series guys picking up the 5d3 and having problems with the AF, black dots, etc... but coming from a 7D background, it's almost identical except more points and a 9 point cluster... Easy to pick up from in that case.
#4 There is no mention in the top LCD for image save method (jpeg L or RAW)... That was one of the only reasons I ever used the top LCD and to see how many approx shots I have left to a card. The jpeg/raw/both setting is no longer present in the top LCD and you have to actually go into the menu to find it. Also another quick access menu that was buried deep within the main menu is shooting styles. 99% of the time I never use it or set it and forget it, but the menu buttons in the back doesn't provide a quick one press access to it. Of course I set it (for whatever jpegs I decide to shoot) so I likely will not touch that menu for the remainder of my days unless I need a saturation boost for whatever reason, but that's neither here nor there, but likely in that situation I may shoot raw..
#5 speaking of raw, developing in DPP with a 16bit tiff raw, you are getting around 110MB files give or take. Developing in 8bit is smaller, but just to think, lets say you develop 10 of those puppies, that's over a gig of HD space right there... 100 of those is over 10 gigs... 600 (typical wedding photographer on average) and your looking around 60 gigs if not more. Just something to chew on... I can only imagine the damage the D800 would do to my HD plus extra workflow but that's another topic for another day.
#6 HDR I love the idea of it... I never really heard it really explained or saw videos of it but always hear that it does a good job handholding... I kinda thought they meant they handheld it and manually fired 3 consecutive shots... nope... set its perimeters, set the scene up, and click the shutter once and the camera rapid fires 3 shots back to back to back without you even thinking of it. I've got to play around with it, but for those down and dirty quick HDR shots for lets say real estate shots, especially on tripods... If done right and with a big enough bracket, it could be a time saver right there... Still need to play around with it and i'm skeptical on how it would handle on a 180 or 360 pano head with HDR, but for a 1 shot application, it's promising.
#7 body... I've heard that it's like full frame version of the 7d. The 7d when I first got it, I was slightly turned off because it was so sculpted. It was very masculine on how sculpted the grip was, where the MFN button and dial wheel was, where the card door holder protruded in the palm of my hand. The card door boobage is still there, but it feels more comfortable (either that or my hand is more used to it). The camera doesn't look or feel as sculpted but more natural and curvaceous. It just feels more comfortable in the hand overall. The grip feels deeper albeit ever so slightly so my fingers when wrapped around touch the body ever so slightly and comfortably. On the 7d, for whatever reason my fingers ran out of real estate in the grip causing the knuckles to buckle a bit and kind of made my hand cramp up quicker (and i've got short fingers, so that says something). The body just feels right in my hands, no guarantees for those with longer fingers though. Anyways Good luck to those who have or are getting the 5d3 and hope to have some photos to you guys soon.