I felt no temptation to send DS to preschool despite the fact that many of his "buddies" were heading there. In fact, I remembering feeling quite liberated by the fact that we opted out. And by the time the "other kids" started kindergarten, it barely made a blip on our radar. I felt if we were truly following an unschooling path, then preschool seemed a rather antithetical choice. Indeed, this was the time when unschooling started to feel 'official' and as such, very exciting and fun and easy. Wouldn't have missed it for the world.
As for DS, he never registered that he was any different because he didn't attend preschool with other children he knew. He always sort of accepted that each family does what they do and this is what we do.
We did have a small, relaxed h/s group at that time that we attended once per week... mom's took turns hosting, etc., which I imagine was helpful but in general, we've never been huge joiners and haven't taken participation in any h/s coops or such. We just wake up, and live our days. DS has never had interest is going to school. DS is very much a "follow the beat of his own drum" kind of guy and I know that school would be ill-fitting for him as AnnaKiss was mentioning of her DS. When I explained to DS about school and what it's about, he was clear about this as well, "Mom, I feel really lucky that you and Dad decided to homeschool!"
DS doesn't have a huge group of friends, but a few close ones he loves to pieces. Of the 7 or so I can think of off the top of my head, 5 attend school, 2 h/s in a more formal fashion. They discuss the differences very little and school (whether you do it or not) has never been a huge issue for any of the kids... because they're to busy playing to care to discuss it.
The best in whatever you decide.