I just recently acquired a Harig 612 hand-feed. I've been looking for one for a couple of years now, waiting for the right price and distance. This one came in at $400 and 40 miles, perfect. The flat way shows some wear (flaking partially erased) at the ends, but otherwise they are in very good shape. The lube system was not working, had to get a new pump. It now occupies the space where my radial arm saw used to live.
I've been doing a fair amount of milling at the limits of the capabilites (precision, flatness and finish) of a BP type mill. The grinder has shown me just how imperfect that work has been. I've been acquiring the accessories, grinding vise, magnetic parallels, v-block, wheel dressers etc. They haven't been that expensive.
For the work I'm doing, a SG has been a valuable acquisition, and not nearly as expensive to tool as a mill.