I am really happy with my decision to build the 50" square KRMx02.
I bought Michael's plans and was very skeptical. I figured I would be on my own because this clearly his hobby job (my going thoughts without experience). I have no experience in mechanical machining, CAD, or anything. I'm a computer engineer who is a living example of the blonde stereotype. But I have some really sharp friends, one is a PhD candidate in mechanical engineering and works at NASA. He's the long pony tail type who machinists are actually friends with because he's one of the few engineers that can bridge the gap between paper and real life.
I give you you all this information just so you can truly understand how incredibly easy and well designed the KRMx02 is and how helpful Michael and his forums are.
My Mechanical Engineering genius came over to check out the design and help me lift the X gantry onto the machine. This is a guy who has a 8'x24' water jet, some large 3 and 5 axis CNCs (watching the tool change on the 5 axis is crazy cool), and some huge 4 axis lathes. He was really impressed with the design, said that it was so over designed for rigidity and so many points for adjustments that he wasn't surprised when I said people in the forums were getting 3 thousandth repeatability.
He and I volunteer on a high school robotics team and have access to 2 4' square CNC machines there that use the V groove system, mdf bed, and water cooled spindles. But he said there was no way he would try to cut aluminum on those. When he looked at mine, he said we have to get it done before the new year so we can use it to mill out our aluminum chassis.
So in summary, the 50"x50" KRMx02 is a $15k machine for 1/3 the cost. The forums are tons of help with great people who won't make fun of your lack of knowledge, instead they teach you. There is only 1 time where I had to wait more than 12hrs for a response from Michael, and I'd bet money that he was on vacation or sick. He is dedicated to helping you be successful and full of wisdom and knowledge.
If you don't like the 6" Z travel, like I initially did, I would encourage you to listen to Michael and others and build it stock first, then after all that, you can make an upgrade. There are so many factors to change, I am only now seeing what will need to be beefed up. But I can't see a need to do this now until I'm ready to add a rotary axis. But even then, I can get by with out more height unless I need to turn something bigger than 4" OD.