I've found it depends what application you're using. For delicate "can't screw this up" work (cabinet doors, face frames), a relatively slow Rotex speed works well - it's much more aggressive than random orbit, so the work still goes quickly. For larger, flat surfaces (baseboards, or cabinet drawer fronts - or for what Matthew is doing), a bit more speed is not a hazard; for preparing smaller parts, I slow it down to maintain control.
I haven't had control problems in Rotex mode - the trouble starts for me in random orbit at slow speed. Almost like jumping - sometimes rather violently! The faster the speed, the smoother running. Still open to tips on this.
Incidentally - a couple of years ago I used my older model 150 to do a quick takedown of paint on my front porch (old t&g). It was totally awesome! I wasn't after a beautiful, stainable finish, but I think the whole porch was done in about 90 minutes. I'd recommend it for sure.