Slow? Are you kidding? They can turn on a dime in tight quarters. I saw a demonstration video when I was in the Army that made me admire the hogs. If I was a tanker and saw one of those bad boys in the sky, I'd park my tank and make haste in the opposite direction!
Was it an A-10 or the newer version/number? My stepson trained on A-10's and we went to every parent's day at the base and they are slow as can be. Maybe they turn quickly, but they move pretty slowly in general, especially compared to other aircraft. They're tank killers though :-)
Slow is a virtue when one is plinking tanks and other armored vehicles. And they are slow. That fat wing can't go much faster, even if you added a third engine (something the Air Force looked into in the late '80s or early '90s). But it can carry lots of bombs, and that big gun is a whole other thing.