I think it was awesome. I grinded it out really hard the first 2-3 weeks, and then dropped off a bit after that. Once you hit the end game and can get 20 kills of the same boss in the same inventory, and get most of the easier tasks out of the way, I feel like the fun drops off a lot. I just got past 20k pts and now I have a hard time finding the motivation to play it, but it's introduced me back into the main game at the same time.
What I'm trying to say is that, overall, the earlier stages and building your character up was some of the most fun I've ever had with runescape period, but that faded away fairly quickly.