I like to model everything in 3d view if possible. Currently I can do that in Rhino, mainly because elevator mode requires a ctrl-click.
I understand the thinking behind a no keyboard requirement workflow, but I think that for something fundamental like this we should at least have the option to constrain the height with a keyboard-button click combination.

At least for me that I don't use, nor will I ever use a tablet that is a definite workflow killer in an otherwise awesome and well thought -out interface.