I Always turned it off, mainly because in crowded areas the bot wouldn't stop pulling mobs along his way. To me, that looks suspicious, because no one on earth would pull every mob in sight running from one point to another.
I also have it turned off. It really takes alot more time to hit 90 with it turned on. I also think it's a BIT supicious, but I don't think someone will report you because you're killing the mobs on your way. I've done that alot while leveling by hand (Sometimes when there were just a few % left to levelup e.g.).