Did you totally freak out like me and think you were playing Oblivion for a second?

No.

I did however, totally freak the fuck out when it was revealed (spoilers, duh, seeing as topic title refers to doing the quest past tense) that Harold The Mutant was that tree thing, and worse, he's fucking dead depending on how you did the quest (whether it's the official ending or not, Harolds sitll rooted to the spot) and that pisses me off, Harold was my favorite character in the whole Fallout universe and as much as I loved Fallout 3, what they did to him is absolute bullshit.

I loved it myself.
It's nice to see the colour in contrast to the wasteland, it's a pity there isn't really any reason to go back there. It's still nice to travel to from Megaton for xp every now and again though.

I liked that there were so many ways to complete it. You could accelerate his growth, slow down his growth, stop it all together, kill his heart, or burn him down. Awesome.

I love it.

Probably one of the best side quest in the game.

as soon as i killed the guy in the church with the coordinates i went straight to it, loved the mission

That was an awesome quest. It gave a lot of personality to the game and Harold as the tree was great. However, I went down to the bottom of his roots and accidentally pressed the wrong thing (I wanted to actually kill him but I ended up planting the Sap that stopped his heart; I wanted to put him out of his misery). Still, great quest. Oblivion-esque in a sense, yes.

The devs must have been smoking something because that place was messed up.  It was very cool, but incredibly random.

I loved that quest, because no matter what you did, you felt like a jerk.
 
But no, I didn't get any Oblivion deja vu.

Probably my favorite quest in the game. I didn't feel like I was playing Oblivion, though, but it did freak me out when I tried talking to the tree (from the back) and Harold said to come around. I did and I saw that the tree had a face and I was like "WHOA!!"
 
But that was an awesome quest. Harold was awesome but I hadn't played the first two Fallout games so I didn't know his whole backstory.

" Probably one of the best side quest in the game. "

"Are you kidding? There's nothing like toasting them with a flame weopon, and eating on the run. YUM! "

I did not think of Oblivion.  I did however find it to be one of the coolest side quests in the game and I caught myself laughing out loud when talking to Harold