Matt,
Unfortunately I cant download your file (or indeed any from the swamp) while at work as my employer's firewall tells me "This request blocked as a risky executable file download. " so its difficult to determine where your choppiness is coming from.
Having done a fair few walk-thrus I would recommend drawing your motion paths with as few vertex points as physically possible, even after spline-curving complex paths, the subtle angular deflections along the path can still induce camera wobble, even if the path seems very smooth to the eye. For example, rather than snapping to the nose of each stair tread, pick 1 point at the top of the stairs then 1 point at the bottom.
It also helps to keep your camera path seperate to your target path, this usually requires breaking your full animation into a serious of smaller scenes, it's more effort but the smooth results are usually well worth the extra effort.
If you haven't already, try the following code, I wrote this a few years back to create animations in Acad. Acad2007's new motion path animator is surprisingly similar
http://www.theswamp.org/index.php?topic=8775.0<edit> fixed that url for ya. Mav
