OP- I'm the pp who mentioned that I thought social skills groups are more of a long term proposition. As for whether they are useful, I agree with posters who said it depends on your kid.
My child has mild/moderate ADHD, very little social awareness/ intuition, and an exceptionally high IQ. He's not deliberately oppositional (notice I use the word deliberate

outside of normal bounds, and is highly social-- wants friends and approval.
Social skills therapy is proving to be effective- we're combining it with behavioral therapy over the summer to work on better impulse control.
Honestly, I have seen kids more impaired by their ADHD and yet, more socially savvy than my DS. I think my DS has issues with social pragmatics that are independent of his ADHD which makes this kind if therapy especially helpful.