I saw the thread on using CR splines using keyframes, but these splines are easy to program for scenes where the geometry is well-known.
I made an experimental movie where the Eye moves around a closed-loop spline, and the Target is the combination of the tangent to the spline, and an offset in the y direction.
I made no attempt to visualize the spline itself.
See
http://www.josleys.com/show_gallery.php?galid=355.
Somewhere on my to-tinker-with list is passing a boatload of camera keyframe quats in a float texture to the shader and indeed have the shader interpolate. Might Make for a nice demo reel.
Would make it harder visualize that path though. Which really helps for those pesky spline over/under shoots on zooms.