Pro's for me:
1) It's easy to learn on, just use someone elses car.

2) It is very hard to get "Bad" results even if your new to it.
3) It's a time saver, IF you know how to use it properly as lil goat eluded to.
4) The
Rotary part of the Dual Action builds up enough friction to break down polishes corectly, unlike an orbital buffer.
5) The
Orbital part of the Dual Action helps it not to burn your paint like a rotary buffer.
Cons for me:
1) Too much use will cause your hands to go numb!
2) A little more pricey than your average buffer. Orbital $20, Rotary $60, PC 7424 $150 (but you can find it online for $105 if you shop around).
Tip: Throw the side handle away. You get better control and can get in tigther spaces with out it.