Actually playing around with it the behavior was very different from what I expected - there was much more zooming. Turns out I missed some parts of the zoom code:
Their zoom actually is my "y" rather than a scale factor, so the metric is ds^2 = dy^2 + (C-y)^2 dx^2 where C is a bit more than the maximal zoom level. There is some special handling for cases where their curve would want to zoom out further.
Normalizing to the same cost to pan all the way zoomed out (zoom=1), their cost for panning is basically flat once you are very zoomed in, and more than the hyperbolic model when relatively zoomed out. I think this contributes to short distances feeling like the viewport is moving very fast (very little advantage to zooming out) vs basically zooming out all the way over larger distances (intermediate zoom levels are penalized, so you might as well go almost all the way).
Their zoom actually is my "y" rather than a scale factor, so the metric is ds^2 = dy^2 + (C-y)^2 dx^2 where C is a bit more than the maximal zoom level. There is some special handling for cases where their curve would want to zoom out further.
Normalizing to the same cost to pan all the way zoomed out (zoom=1), their cost for panning is basically flat once you are very zoomed in, and more than the hyperbolic model when relatively zoomed out. I think this contributes to short distances feeling like the viewport is moving very fast (very little advantage to zooming out) vs basically zooming out all the way over larger distances (intermediate zoom levels are penalized, so you might as well go almost all the way).