My son was offered a 2 to 4 skip for next year. We declined it in favor of a new school that groups kids by ability. He's very excited about this school. He's spent a couple days there and came home very excited about what he'd learned.
Even though we declined, the school was good about giving him 3rd grade books while he was in second grade. From what I could tell, no one got wound up about it or even commented on it.
A boy in his class this past year had skipped K to 2 and he was accepted pretty easily by the kids from what I saw. They're still very young at that age, which I think makes the grade skip easier.
I remember that a kid was held back in 4th grade when I was in school. He showed up in our line on the first day of school and we asked why he was standing with us. When he told us, everyone said "oh" and that was the end of it. No one ever teased him. Sometimes (not always) this stuff is a bigger deal for the adults.
If people are interested, I'll report occasionally on how well the ability-grouped school goes. Really, I think this is the way schools should be run: figure out what level each kid is at, and group them that way. It would work best for everyone.
Val