I once cut plywood a wind turbine blade on my milling machine with a TCT router bit, long before I'd made the CNC router. Due to the potential problems from the dust I taped paper to the machine to stop the dust getting on the slides too much, then cleaned and oiled everything thoroughly afterwards. The chipload can be kept quite high - I used something like 0.2-0.3mm chipload at 2150rpm. I think it was a 1/2" cutter. The milling machine is obviously very strong compared to a router, so you can push it quite fast. Not something I would do remotely regularly though...