Once you add that new path, AutoCAD will add a new "Add-A-Plotter Wizard" shortcut to that folder automatically for you.
This is great for sharing your pc3 files but the properties of that shortcut also point back to the local hard drive to the installation folder.
If this folder and .exe file do not exist on another machines hard drive (i.e. 2012 isn't installed on the other machine) then it can cause performance issues. I've seen it take 5-30 minutes just for the Plot/Print dialog to show up on the screen. Same issue with the "Plot Style Table Search Path" can happen. These invalid shortcuts can cause really bad performance issues. So, how do you get around it? You have two options: 1) Delete the shortcut 2) Install the updated program on all the computers. Now, if you install AutoCAD 2012 and someone else installs Architecture 2012, those install paths will be different and one of the two machines can have problems.