Plot formatting is by far the weakest point in Mathcad 15.0. It took years to get even the capabilities for movable legends, hidden axis variable, and titling and axis labeling. Prime needs to follow suit and, to be really useful, go few steps beyond. Look at any high school or college engineering requirements for an acceptable plot and you will see the following:
1) Descriptive Title
2) Axes Labels
3) Axes numbering (both with a sensible interval between ticks and a readable font)
4) A legend - and legends don't go on the axis! (Let alone, on both!) They can be to the right or above/below the plot frame, but modern publications expect them to be embedded somewhere on the plot.
It's been three versions of Prime and we're not even meeting the basic requirements of a 2D plot! Presentation is everything! You can solve the most complex mathematical problem known to man, but if you can't present it, you won't be able to get your point across. Read any of the books by Edward Tufte on graphical presentation of data - THIS IS IMPORTANT! Mathcad and Mathcad Prime must have the flexibility to present data in a meaningful way. Of course, data can all be exported to another program and the plots can be made there, but this creates extra steps and does not allow Mathcad to be used to prepare a publishing quality document.
I suggest getting Prime 4.0 up to speed with Mathcad 15.0 and giving your useers a few tools (infinitely placable legends, font selection and sizing on titles, lables, and axis numbering, numberical format choices on axis numbering, etc.). You will have VERY happy users. I myself might even quit using Mathcad 15 altogether...maybe. This is a "gotta have" on my list. These features should also extend to other plot types.