I have done all the DLC, Main Quest etc. I found the quest in Oasis to be the hardest choice I had to make in FO3. I chose to activate his heart so it would spread the seeds faster and farther. I realize that I was quite possibly dooming someone to live for centuries who didn't want to. Luckily he (Harold? Bob? HA) seemed cool with being "god" for these people.

As for "why" I felt that his influence on the wasteland would be irreplaceable even if it meant that he has to involuntarily suffer to do so. It wasn't an easy call to make.

I was so close to killing the poor bugger though. How did you finish the quest and why?

as I found the tree minders utterly useless and not contibuting or sharing there resources...
I killed them all...
left Harold alone though... pure bastard..

I did all options :/

my final chocie was to speed his growth ... i was in it for the loot

I too, thought long and hard about this when I first came across this quest. I chose as you did. Harold seemed okay with it when you explained it to him, and future benefits will be vast for thousands if not millions of people. I just wish we could have seen some sign of our choice, in the CW. Nothing big mind you, just.... something.

EDIT: My evil character cleared the place out, and it's now HIS Oasis in the desert.

It took me forever to decide how to do this quest the first time around. I ended up shooting him as that was his wish but I always felt terrible about it. Since then, I usually accelerate his growth. I was quite surprised how well he accepted his fate. I can't say I would have taken the news quite as well. I would have pulled up my roots and strangled the Lone Wanderer with them.

I saved him too... i think this was one of the better written quests of FO3... Love the poor bugger...I go from time to time to bother in a RP way... second favorite char behind No Bark from FNV

first time i killed him, hard to resist his plea.

I like to side with the tree minders that want to share him or this resource with the wasteland, so I accelerate his growth. I also prefer the rewards you get for doing it this way.

After having met the guy in FO1 and FO2 I felt obliged to help him out. Or at least not set him on fire.

Helped him die.

I honestly didn't think it was a hard decision. I destroyed his heart without hesitation.

My good character have a hard time doing anything other than accelerating his growth. Which is difficult because I think killing him gives the best reward. But killing him doesn't seem right.

Took me a while to decide but I killed him. By far one of the most well-written quests in fallout 3. Leaves you with that 'what if?' feeling afterwards.