Hi,

I did both for many years and still do so without any problem. Why should there be any issue with reliability or accuracy (as long as the drive is not overloaded)?
Its a convenient way to save cost (2 motors @ 1 drive) and / or output pins.
There is only one - theoretical - drawback: you can't reference both axis independently. "Theoretical" because if you have a double X axis configuration you need to be sure they stay in sync - if not you're in trouble anyway no matter how the motors are connected.