I do think gifted kids can enjoy a standard preschool classroom, but that doesn't mean it's the right fit for all of them. My older two boys each attended an NAEYC accredited "child's day out"/preschool. They both loved it for various aspects. They got to paint daily, had different toys to play with, a big playground to play on, and kids their age to play with.
My eldest son has a March birthday so finished up at the school when he was just over 5. He was evaluated, as they all were, for skills he'd demonstrated throughout the year, and the teacher was quite confident he would be just fine to start kindergarten in the Fall. I had to laugh, because he was SO far beyond their skills academically, yet she had not had the need or ability to recognize his true levels on things like reading. (And, um, yeah, he did just fine for K at home!)
With my 2nd, born at the beginning of September but missing the local "cut-off," we took him out of the school after his 3/4yo year, which was a huge shock to all the teachers and parents. He didn't need another year of learning basics, as he was already reading, doing math, and showing every sign of readiness for in-depth learning that he could. I considered leaving him in for the socialization, but am happy to have brought him home.
They do both have fond memories and didn't suffer for being abnormal, but if that's not a situation your child would thrive in, I don't see any reason to pay for it.