Brendan,
Very true. Many people think (and with good reason!) this is the ideal (and only) solution for DIY scopes and retrofits.. it uses low cost and various h/w (Arduino) and open-source f/w - the best possible combination.
Myself, I tried many systems in the past (Bartels, Soundstepper, AstroEQ, PICGoTo etc..), and now I have OnStep on both my EQ6, EXOS-II, and Dob.. and I retrofitted my friend's Nexstar mount (MEGA+RAMPS14).
For my dobson mount, at first I went from Bartels to OnStep because one of the Fujitsu st1000 tablets that was running Bartels started to freeze, so I decided to better replace it with more available hardware running OnStep (Arduino MEGA was my first choice then, now I have it on ESP32).
Sometimes I had problems (most of them were me not reading docs on Wiki carefully enough!), but the support from OnStep community was always great and everything was usually sorted after couple of posts on
forum.