I'm with Angie - it all depends on the details. For me (smaller frame, square but not broad shoulders, small bust, long neck, short waist) it can work really well if the shoulder drop is not too extreme, if the top is shorter (as Carla suggests and Chris's examples show) and -- crucially -- if the neckline is neat. A wide loose neckline will make the top slide around all over and feel awkward and look too casual and/or messy.

What I like about dropped shoulders -- if the fit is good, they are comfortable, easy to move in and convey an impression of ease and "cool."

Some that work in my closet...

Note, I am also a fan of a fitted shoulder. And a dolman sleeve or raglan sleeve. Again - it's all in the details of the specific garment.