When I was first getting into Metal, Ozzy Sabbath was the only Sabbath I listened to. I don't remember where along the road I was exposed to Dio Sabbath, but I never turned back. For as long as I've known his material, Dio has been my favorite of the Sabbath vocalists, which is why my fondest (and only) live Dio memory is of seeing him with Heaven and Hell (the only live incarnation of Sabbath that I've seen), with Alice Cooper and Queensryche opening.
The Massachusetts date was at the end of Locobazooka, which was a local festival (I believe it's relocated since). Tons of bands played throughout the day, and many were awful, though I remember Meliah Rage also putting on a good show that day. There were three or four stages set up in the parking lot area of the venue, but all three acts on the H&H bill were set to play the amphitheater stage, and as the only acts to play the stage it almost felt like it was a separate show together.
It was a surreal experience. I'm wearing my shirt from that show today, actually. I never thought I would get to see Dio front Black Sabbath live, and getting to witness it first hand was amazing. I admit, I feel foolish for the many times I've passed them up - I believe there was a local date for every North American tour they did. But atleast I got to see him the once, to hear some of my favorite Sabbath songs performed almost flawlessly by a top-notch act and phenomenal vocalist.