Aah well there aren't any cons of it yet, just that it feels sort of funny whirling a noisy device over a wet car. I found it useful in many aspects, in addition, it helps me clean split ac fins, my PC's GPU fins, laptop keyboards and most importantly, I can sue it while closing (DIY opened) headlights to whizz off any dust particles inside.
But hey, those are pros of the little friend.
In detailing, you can get rid of water from door hinges, number plate garnish, chrome badges, side moldings, side view mirrors (which drips with time if it stays and causes PIA), in the engine bay you can usually keep it clean by daily whirling it inside unless its been driven in mud/rainy water, water in the wheel nuts which causes fugly rust with time is also not a PIA anymore if you have a blower.
bow