To start with I previously built a Joe's CNC 4x4 Hybrid. The machine used leadscrew and flange bearings to move the steppers at around 300 inches per minute. I had roughly 52" of Y axis travel and about 49" of X axis travel. Unfortunately, the Y axis tended to bind in the last 2 inches at the front of the table. This was purely due to my building and not a fault of the design. Therefore, I tended to think of 50" as being the most dependable figure to use for travel.
My son Benjamin and I completed the table in August of 2009. I used MDF in many places that called for Plastic in the original design, because The router I used to make all the parts was unreliable and I didn't want to risk my expensive plastic sheets.
I was really happy with the Hybrid's reliability. I cut a few projects with the machine and was really enjoying myself with my new hobby. However, as I mentioned earlier, people are constantly innovating and I like life on the bleeding edge.