By far...
Haha, and Sam's hair:D

They were both so sweet and caring, and they were BROTHERS! I don't even know what kind of a relationship they have anymore.

Pretty much everything.
I still love SPN, but it's getting way too dark and depressing for my taste.
I definitely miss the older seasons.

Well, actually... Not having Sam's forehead staring me in the face every episode. :P

ROFL @ nevermind606! I agree. Jared needs to do something about that mop of hair. It looks .. not good. It makes his face/forehead look bigger.

I love seeing them set the groundwork for everything to come. I love the earlier seasons but I never look back and say I wish things were the same as they used to be. If they were, this show would be boring.

What fanfly said.

Although I do miss the brotherly love/the teamwork.

Hahahaha!!! I agree he needs a hair cut!
I love how innocent they were and Dean's voice and scruffyness in some of the first eppys!

Their innocence and their brotherly-ness, the general family vibe of the boys getting to know each other again and working out how they can fit and live together. I miss their hunt for John the simplicity of trying to find their dad (compared to saving the world) whilst it being one of the most complicated things they have done together because they are lost and alone.

I really love the boys innocence. Lol and Sam's hair was adorable :D

One thing I note is that research actually takes some time. These days, it's just calling Castiel or Bobby for exposition.

..that and Sam's hair. It's fine now, but he was so adorable with those bangs.

I love how their biggest worries and problems were YED, Meg and other demons. Also Sam's hair. Sometimes I watch the earlier seasons only for his god damn adorable hair ^^, ♥ I think his hair is great now though!

and totally Sam's hair xD
the hottest sam was in Season 1xD

and seeing the groundwork....and their innocence :)

and sam's HOOOTTTT hair lol

All of these are good points (except the no angels part, cos there was no Cas!) but this one I agree with most, because it's so interesting to watch it and go "Oh that totally explains why that happened" and "OMG it all makes sense now!"
Especially what Gabriel pointed out about Dean/Michael = the big brother, loyal to an absent father and Sam/Lucifer = the little brother, rebellious of Daddy's plan.

and I miss Sam's hair =/ But Jared is stil HOTHOTHOT <3

Sometimes I miss the easy jokes and almost carefree innocence of not knowing that they are Michael/Lucifers vessels and all the Hell (literally and figuratively) they are going to have to go through.