It wasn't even relatively happy to me; it was a full on tragedy. No one got what they wanted and it ended all sad. So yeah, tragedy.
Dean isn't one for a normal life, no, I agree. I just hope Sam gets to him before he starts getting too attached to Lisa/Ben. :/

Eh, maybe. I would have preferred he didn't go to her either but I'll be completely honest in saying that if it was a choice of him going to Lisa or being suicidal and just not caring to live anymore, then I would have to choose Lisa.
Sam...who knows what he's going to. I could see him hunting and maybe coming back to check up on Dean a few times. It'd basically be the reverse of Sam at Stanford living a normal life - which, is kind of ironic because it really is going right back to the shows roots then and where it all started.
But it's just the 'And this is the last time Dean would see Bobby for a long time' that worries me. I mean, how far of a time jump are they going to do? :/