Do disposable pans affect the quality of pies baked in them? I'm worried that using a disposable pan may adversely affect the end result.
Yes, they turn out just fine.
As with any pie pan, if it isn't the pan you use every single time, you need to be aware that the surface on the bottom of the pan, and the material it is made of, will be a factors in the browning rate and cooking time of your pie, so keep alert. Even expensive high quality pans will behave differently from each other in the oven if, say, one of them is glass, and another may have a black metal surface, or maybe another has a shiny reflective finish.
The fact that a pie pan is an inexpensive disposable one is not relevant. It would behave just like a fancy name-brand pan that was lightweight and shiny.