I just got my 7D and dropped off my 50D at the same time. Having played with it for about an hour now, here are my very very first impressions when compared to my 50D.
Weight, handling & appearance
The camera does not seem noticeably bigger, but the added weight is definitely noticeable. The camera does feel more hefty all around. The various chrome trims around the lens mount, top dial, back dial etc. do seam slightly tacky, but I'm sure I'll get used to it. When comparing it to the 50D the addition of the various buttons becomes immediately apparent and makes the 7D feel cluttered.
Button and button layout
Compared the the 50D, my very first impression was that the buttons feel "squishy". They seem a bit harder to press overall, but seem to be more soft and don't provide the "click" feedback that the 50D buttons gave. This also applies to the shutter button itself. The reason may be the added weather sealing. I can't judge yet whether this change is good or bad, but it's definitely different. Something to get used to.
The new M-Fn. button is located well near the shutter and should provide nice additional control options. It is used for selecting the AF point mode which wasn't immediately apparent to me (no, I didn't read the manual yet).
The location of the top LCD light button has switched making it the far right button now and the ISO button #2 from the right. I don't like that switch at all! I use that button a lot while looking through the viewfinder and having it on the far right made a "no look" access much easier. This will also take getting used to!
CF Card slot
I read somewhere that the 7D also takes CF micro-drives? I'm not sure whether this is true or not, but it may be the reason that the CF card slot on the 7D seems to be "larger" allowing for thicker cards. This made inserting the CF card actually a little bit more fiddly than on the 50D. I do usually use USB to transfer files so I probably won't notice this, but I have to say I liked the 50D's CF card slot better.
Menus & custom functions
The menus on the 7D are a big step up from the 50D in my opinion. The functions are much more logically placed (flash control for examples) and some custom functions have been elevated to actual menu entries to make them easier to access.
Also, some custom functions, like the one to assign which button does what, now have a graphical representation of the camera to locate the button and show an icon for each button as well. This makes some of the C.Fn. much easier to use. I like this change a lot.
Flash control
I did try the flash control and it works quite well. The controls are well laid out and in my quick cubicle tests the flash performed well. Very happy to have this feature!
Auto focus
My main shooting discipline is youth soccer. So I can't comment to much on the new AF until I get to a game. So far, it worked well though. The AF point selection feedback is good and it locks on very quickly even with my 50mm f/1.8. The AF Mode selection seems a bit counter intuitive since it involves using the M-Fn. button. But once you know it, you'll get used to it.
ISO performance
The real ISO performance test will be my next night soccer game. So I can't really comment on that yet. Though I do have to say I tried a shot on ISO 3200 and it looked great on the LCD! I had hoped to get another usable (to me) stop of ISO performance out of this upgrade and so far I do think the 7D delivers. Devil is in the details of course....
Viewfinder
Sweet!
,,,just kidding,,,,5d goes no place i dont go
