Yes, I have an M13 and Unicomp EnduraPro. The M13 has a real ThinkPad-style TrackPoint and works well. Unicomp uses a weird resistive strain gauge in a loose plastic housing and doesn't work very well at all. The M13 has a fairly thin plate...about what Unicomp uses now. Except for the fragile area around the trackpoint buttons, the case has your typical Model M feel and heft to it. The Unicomp has the noisy/squeaky plastic shell.
My M13 is in pretty decent shape, but I would not pay this much for one, even NIB.