I say NO!
My Eldest son went to preschool. I had a Happy well behaved little boy, and a few short months later I had a child who I didn't know, and had I not know better I would have sworn had ADHD.
Mind you, I never went to preschool, and had no intention of sending my children. I gave in to pressure from the family to send him, and what I found was that, IMHO, preschool isn't socialisation, its a place where fed up mums drop of their brats for a few hours peace. Children at that age are not capable of meaningful socialisation without constant supervision and I’m afraid the preschools in my area just aren't up to watching the children, or fighting a losing battle with the parents to discipline the naughty ones.
It took me 6 months to get my son back to a boy I recognized, and even now he carries memories of having sand thrown in his eyes there, something I didn't find out about until after he'd left.
I’m sure a preschool could be a positive place, and I’m sure a lot are, but I really don't believe that they can do anything there that you cant do yrself, with out the risk of them not being correctly supervised, and like I was lied, to about what was happening when you where not there.
None of my other children have gone to preschool, and none will. My oldest daughter started full time school a few months back and she has settled in just fine, without going to preschool.