It really depends on the trainer. I took Loki to a training class at our local PetSmart and we had a good trainer. She still remembers his name today when I run into her at the store occasionally, and he apparently still remembers her, because Loki goes nuts whenever he sees her.
My class was relatively free of distractions, though, as it was on Tuesday nights around 7:30, and Loki was the only dog in the class who made it to every session. Two of the nights I was the only one there, so I basically got a private lesson.
The class didn't teach Loki anything I couldn't have done myself, but it was still a good excuse to take him to a strange place and work with him there, often around other dogs. I'd definitely recommend at least checking out a class, or meeting with the instructor at least.
Also, I believe PetSmart has a policy that lets you get your money back after the first class if you're not impressed. I could be wrong about this (it's been six months since Loki's puppy training), but it's worth checking into.