A "gradient" mode would be quite nice, yes. I would point out the obvious, though, that gradients can be both positive and negative when the track is viewed directionally. This can be handled nicely by having two coloring modes: one where positive and negative are colored differently, and one where they are colored the same. The same track can then be viewed in terms of directional grade, or in terms of absolute grade.
As for colors used, I would like to be able to change them. Most of the colors used right now in the elevation coloring show up pretty well, but the white used at the highest elevations often fades into the background on my monitor. It'd be nice to define my own rainbow, to match my usage better. Of course, with my recent record on asking for features already present, this is probably already possible. :roll:
Smoothing in raw elevation mode could be useful to eliminate bogus points. Maybe the algorithm used in your Climbing Analysis could be adapted. So long as we can turn it off...
Finally, it would be nice to be able to specify elevation limits and defaults. All recorded elevations get clipped to the low and high limits. All unknown elevations get defaulted to either a fixed value, or to the elevation as pulled from available DEM data (IIRC, you can insert the DEM elevations into the track already, so this is just a non-destructive version of the same idea). Similarly, an option to ignore the recorded elevation, and use only the DEM data could be useful.
-- Mark