Claris CAD 1.0v3 and higher attempt to utilize the full accuracy of the plotter and will send information at a resolution which matches the capabilities of the configured plotter. This can vary from 254 to 2032 dpi. Unfortunately, MacPlot is unable to benefit from ATM when printing at this resolution. Instead it will scale the largest size of the font you are using. As a result, your Postscript fonts will be smoothed on screen but will plot with jaggies.
Note: Restricting output to 72 dpi from MacPlot Professional will not allow ATM to smooth your plotted text. Claris CAD would need to send information to MacPlot at a lower resolution for ATM to have an affect.
MacPlot Professional v3.7.4 addresses this issue.