Previously, I was in the "not worth the hassle to change yourself" crowd, but after several negative experiences with my jiffylube, I changed my tune.
On one occassion, the kid cross threaded the oil fill cap. Fortunately, he didn't torque it down, just gave it a spin and left it.
On another occassion, I brought my car to jiffylub for a coolant exchange. I figured this was a good idea since they have a machine that will suck out all the old fluid. When I got home, I noticed that the fluid in the overflow resevoir was a sickly green and full of scale. The guy obviously put somebody else's crud in my overlow. I turkey basted it all out., but that was the last straw for me.