I'm another MDF router builder/user. Fortunately, I bought the steppers/electronics with a view to building a better machine later so the biggest investment is largely reusable. However, the MDF (plus added steel supports to try to keep the bed roughly flat) and the steel tube/skate bearing runners didn't cost that much. However, they did largely influence the incredibly slow movement of the machine, due to lack of strength and rigidity. The only thing moving faster than the gantry was the MDF bed (and the gantry, and the Z axis platform) warping...

Yes, it can work, kind of, but I'm not sure if it's worth it. It taught me a lot, and the biggest lesson was why I am now building a welded steel-framed machine. Welding (strong if not pretty) is not that difficult, and almost any welding problem can be fixed with a cheap angle grinder and rewelding. DAMHIKTIJKOK?