I don't doubt the veracity of what you're saying I just have a hard time figuring out why sometimes my camera gives me close to 5fps and other times while keeping the shutter pressed it will take 1 or 2, long pause then resume. Unless it's a hiccup in the buffer handling. But I use Extreme III card and I almost never take more than 5-6 shot burst. And, when shooting sports I shoot in JPEG.
So, let me rephrase my original statement to this:
based on my experience of about 30,000 frames shooting action sequences while using an EXTREMe III cf card and taking typically 2-6 shot burst, always in AI-Servo mode I have experienced different levels of burst rate performance. Sometimes I get around 5fps. Other times I get half that. Cause of this is unknown to me. Whether this same scenario would occur in single shot I can't say - my experience there is somewhat less (I do use it for golf where the player's face typically remains in the same focal plane - so based on a thousand or so shots I consistantly got the 5fps performance).