I think it is fun. I can do whatever I want (well not the things that cost too much money, but I don't want to do that atm anyway), and I've done all quests too. I do believe it was more fun starting out and discovering everything, but you can only do that once. If I'd start all over on a new account, nothing would change except my stats, because I already know everything about training skills and stuff. So yeah, I think it is more fun than being a low-ish higher level (70-90 combat) who wants to do everything but can't do anything, but less fun than starting out.