This is the 'tried and true' method for people without a chill tube, and one I use.
Does it work? Yes...
Is as efficent as a wort chiller? - Define efficent? if you mean 'quick' probably not.
Method - in your deep sink - or bath tub - combine some cold water and some ice - lots of ice. put wort in with a thermometer of some kind handy and sanatizer to. (Spray bottle of Idaphor or star san for contact sanitation) Put brewpot into bath, A) swirl bath (with hand) , B) with sanatized spoon swirl wort C) wait. Repeat A, B and C in any order until thermometer shows low enough temp - say sub 80, preferably around pitch temp if you did a full boil (say 70 or less)... transfer to fermentor through prefered method. For me and my sink this is genrally about 1/2 hr with a 2nd bath having to be drawn. Since I've never had problems with flavor or clarifying I just poor it over, but others like to syphon it down. If you have a valve on your pot, don't forget to hit ti with sanatizer first before using.
You might have to draw another bath if your bath gets to hot (ice melts, feels warm to touch) this depends largely dependant on things like how much cold you put the brew pot in and how much you have in your brewpot. A 3 gallon wort will chill faster than a 10 gallon, and a bathtub can hold more water and ice than a sink.
Potential drawbacks? If you aren't careful with your sanitation -the stiring steps - and stiring the wort is really helpful to spread the cold from the edges to the middle of the wort you coudl get an infection, as I said above it might not be as fast as a wort chiller.