My apologies for digging up an older thread, but I have noticed one thing when shooting video with my 5D Mark III and then editing on a Mac/FCP.
At work, all of my video editing is done on a Mac and FCP 7. Normally, I use a Sony HXR-NX5U, which FCP logs and transfers just fine. I'm aware that DSLR footage isn't native to FCP7 and as such, must be transcoded to ProRes for efficient editing. If I can't transcode directly via FCP, I use MPEG Streamclip.
With that said, I recently shot some footage on my 5D3 @ 1080p/24fps/ALL-I. I loaded the footage into MPEG Streamclip (latest build)....and the program promptly crashed. I tried again and got to the export screen, but it crashed again. I then loaded up FCP7 and entered the Log/Transfer menu, to transcode the ALL-I footage to ProRes. Same thing happened-- FCP crashed when trying to bring up the ALL-I footage.
So I went out and reshot the clips, this time in IPB. I brought the 5D3 IPB footage back to my Mac, loaded up MPEG Streamclip and voila: Footage was converted to ProRes MOV files without issue or crashing.
Now, I may be completely oblivious to some work around, or I may be having a "Master of the Obvious" moment, but for FCP/Mac users, I would advise shooting IPB to avoid transcoding headaches.
Of course, if you use Adobe Premiere 5.0/higher (as I do at home on my PC), then all this is bypassed, due to Premiere's native DSLR capabilities