[jgmick]

Gents:

Several comments, first, what I know and then what I think

I have a Sieg, running for about 3 years. Nice machine with some caveats.
Good points: Runs, cuts metal nicely. Pretty much hassle free as long as the operator doesn't do stoopid things. Big enough for me to get useful things done (Yes, bigger is always better)

Bad point (singular) Lousy Z repeatability due to the way they spring loaded the Z axis to take the weight off of the Z leadscrew. Z can move around up to 0.003 inches from run to run. Real pain.

BIG good point. All of the lead screws have ballnuts on them. I would not personally consider any NC mill without ballnuts. IMHO. The backlash problems will eat you alive.

Commentary on open vs closed loop. You probably simply don't want spend the money for a "real" closed loop machine. That feature adds cost like mad. A middle approach adds encoders on the lead screws to tell you if the stepper missed a step. Almost never happens unless you run at real high speeds or have really big cutting loads. True closed loop uses DC motors for drive and glass scales for position readout. That is what the big boys do and you pay big for that.

More commentary: If I had it to do over again I would get a Tormach. Better built, better design, costs more money than the Sieg. If your budget can stand it take a look.