I think it's good for kids to get to be around their intellectual peers, but it's not a requirement for friendship, of course. MY DS is behind emotionally/maturity-wise, and often gets along with kids a couple of years younger than him better than kids his own age, regardless of intellect. When he wants to play, he wants to run and shout and play fight pokemon battles and whatnot.
Of course, I'm not sure he's been around many other children who would count as 'intellectual peers' so I'm not sure how that would even go. With his PDD-NOS, it would probably still end up a crap-shoot.