I can side mill wood, any wood, all day at 700 RPM and get jointer like finishes that require very little sanding. The only time the slower speed of a metal cutting mill is a handicap is when you are trying to get a good finish off of the end of the cutter.
When I do need a good finish like on the bottom of a milled pocket I swing my milling head 180° and presto I have a high speed spindle using my home made router adapter! (old pic)
As far as this oily, grease covered world that some envision with machine shop equipment, that is not the case unless you are running 60+ year old machines with babbit oilers all over it.