To my thinking getting up cheaply and running reliably and having a system that is interchangeable is the way to go. Breaking the bank and getting stuck in a single solution is the last thing you want to do.
Building the CNC mill showed just how frustrating going the Mach / parallel port route as it is complicated. Every mod seemed to take hours to figure out. Granted it can do amazing things, but a simple 3 axis machine isn't / shouldn't be complicated.
By contrast the 3d printer is a breeze. (granted I already have the CNC mill experience.) It's arduino interface is simple compared to the mill. No computer is required to run it after firmware setup is finished, the printer can run by itself. Slap in a SDcard and hit print. I can't even begin to describe how much better this setup is to actually use. I only have a 4 line lcd display with encoder but now people are able to use 4" touch screen full color interfaces.
I am tempted to make a 3d printed model of a router table as a test case. Make something that can take a 8x10 piece of paper and uses a pen as the head or something. I can use printer stepper motors and keep things super cheap to test the idea out. Anything I do buy will be spare parts for the 3dprinter anyways. It's an interesting idea anyways...
If a MDF router table allows you to get up and running easily and allows you to slowly replace it with alum or steel parts then it seems the way to go. Plus you'll be more inclined to make mods/ fixes.
Proud member of MtTABRA
(More than Three Axles Big Rig Association)