Every time I see someone mention tubing notchers and building bike frames, it's always negative. Not precise, have to be aligned/shimmed, won't hold thin tubes tight enough without crimping, etc.
+3 for the vise, block, and file method. You can hand cope a tube just as fast or faster than you can set up a notcher, mill, whatever.
A mill would be nice to have for other things though...think of the stuff you could make!