The rationale for current approach is explained in msg250.

I believe the conversion (e.g., to latitude/longitude/depth and cm/yr) should be
done in a post-processing script. Such a script will depend on some dimensional
parameters (radius of the planet and thermal diffusivity for example). As a
result, different people will use a slightly different script for the
conversion. It is difficult to write a script to fit everybody's need.

A simple script is attached for your need. But it is not general enough to
warrant inclusion in the future release.

in a future release (or patch!) would it be possible to use latitude/longitude
instead of thetas and phi's in radians, at least optionally? i know it's easy
enough to convert ourselves, but i'm lazy and already have a ton of lat/lon
velocity files. plus it just seems more intuitive, at least for regional
computations. maybe i'm missing something.

same with z-- an option for depth in km vs. fractions of the earth's radius
would clean up my code a bit and make the data a bit easier to read.

otherwise i really like the changes made in 2.1. much, much easier to use. thanks!