If you are switching from LCD to CRT and back, you may have some problems.
LCDs do some tricky partial pixel stuff, so this is often a place to watch for.
However, for the most part, and particularly if the screen sizes are the same from one machine to another (I standardized on 1024x768 here in our labs, but hard to do with the big LCDs now available) you should have no problems developing on one machine, and running the EPP scripts against another very similar SUT.
Even changing screen sizes is very rarely an issue. Unless a smaller screen size causes some element in your interface to be displayed at a different size, everything should just work.
It is important to standardize other configuration settings, though, particularly the “font smoothing style” (on the Appearance pane in System Preferences). As Todd pointed out, this setting has different defaults depending on the type of hardware you’re running on, so it’s easy to overlook.