Well, every child is different, so definitly don't judge your son's progress by how other kids are doing
My son is almost 2 1/2, and since I am expecting #2 in April, I decided to give potty training a shot. So last week, I just put him in underware, and told him there is no more diapers (we've been working up to this by talking about the potty ALOT, and occasionally sitting him on the potty)
I am really surprised at how well it is going. I think that pullups are really just (even more) expensive diapers, and that you just have to take the plunge to underware. Is he bothered when he messes in his underware?