I do wish that they would have moved the BULB mode past C1-C3. I use it sometimes, but not as often as I would C1, and the chance that I miss and leave it in BULB is too great.
Not that I have a 5DIII, but I really like that C3 is the end of the dial on my 7D and 5DII. My C3 setting is sort of 'OMG I've got to capture that' setting (birds in flight, etc.), and being able to just spin the dial until it stops. I'll miss that on my 1D X.