I agree with Rory and Urbycoz.
My son has been in daycare since he was about 5 months old, first with a friend of my wife who was a stay-at-home-mom with 3 girls of her own not yet in school, and then with a professional home daycare run by a wonderful woman who is responsible for 6-7 children full-time during the day.
Aside from my son having an early fascination with blonde girls (the mother and all three girls in the first home were blonde), the experiences we've had with daycare have been overwhelmingly positive, despite our concerns.
When we first started, almost all of the children were older than my son. However, with the supervised interactions, the older children provided models from which my son was able to quickly learn how to interact with other children.
Now there are several younger children, and my son has learned the rudiments of age appropriate interactions (he is much gentler with littler children, and knows that it is better to give hugs to an infant or younger toddler than it is to try and play "tag", even though "tag" is one of his favorite games with the older children).
We've seen absolutely no sign of detachment from us. Our son is very affectionate, friendly, and one of the happiest children I've ever met (granted, I'm biased, but quite honestly, he smiles and laughs at least 95% of his waking time). He doesn't get upset when I drop him off in the mornings (so long as he gets his hug goodbye!), and is always happy to see me when I pick him up in the afternoon (although if he's in the middle of doing something with the other kids, he may not be quite ready to stop what he's doing just because I showed up).
He talks quite happily about going to play with his friends in daycare, although he gives equal weight to the other friends and relatives his age that he sees outside of daycare.
We have no problems leaving him with relatives that he knows (his grandparents) at times when we need a babysitter, and rarely cries when we leave (and on those occasions, it doesn't last more than 3 minutes after we're out of sight).
As for being stubborn... well, our son is stubborn, there's no doubt about that, but I do have to question any assumption that daycare is the cause, or even a contributing factor.
The issue he's most stubborn about is eating, and trying new foods. However, in daycare, he eats literally anything that the daycare provider gives to him, and apparently without complaint. For us, it has become a game to try and avoid eating anything new with us, but we're getting past that. However, if our daycare provider hadn't told us repeatedly how readily he eats a huge assortment of foods, we likely would not have pushed so hard for him to eat a varied diet for us, as well, and we would probably have caved in to accepting that our son was just a "picky eater".
So, to address your three main concerns:
1. Does he show detachment from his parents? Absolutely not!
2. Does he show aggressive behavior? Absolutely not! In fact, his cousin, who is exclusively cared for by his stay-at-home-mother, is far, far more aggressive than my son, and his parents attribute it to not having any experience playing with younger children.
3. Is he stubborn? Yes, but daycare has actually provided us tools to help deal with that stubbornness slightly better than we might have without it, and I don't see any reason to blame daycare for the stubbornness in the first place (how many 2 year olds aren't stubborn, anyway?).