This is all by way of saying Bungie bought a lot of good will from me so Destiny will likely be my first purchase. You should feel no obligation to read beyond this.
The Halo 1 campaign was very good, but for me Halo has always been about the multi-player.
I have never had a multi-player experience like Halo 2 and Halo 3. I was 29 when Halo 2 came out. I bought a console just to play it because a buddy had Halo LAN parties and I wanted to be a part of it. I started off so, SO bad at the game. In one 2v2v2v2v2 match on Ascension my teammate and I had a negative score. Not just more kills than deaths, but more suicides than kills. I was terrible.
I fell in with a group of people my age or older mostly to ward off the XBL undesirables. I got better. Eventually I got good and then I got really good, though several levels down from the truly elite. I was able to experience the game from near the bottom all the way to close enough to the top that I could see it. Halo 2 and 3 were like chess games to me, less about button mashing, more about teamwork and strategy. We'd play against other teams of old people that we'd prepare a whole week for. If we ran into griefers or glitchers or stand byers or whatever we'd just wait it out and keep rolling.
There was always the sense every night that we were going to have a game that would have a story to tell. A random teammate whose incompetence or quirk we had to overcome, a particularly compelling endgame, a teammate that went beastmode and dominated the game.
I've tried other games, but I have never matched that experience. Where Halo felt natural, with other games I've always felt like I was controlling an avatar. With Halo I could always tell how I died, with others it was always a mystery. Games were chores, the players all looked alike, everything felt very samey and except for COD there was never that critical mass of players necessary for a really varied, exciting, evenly matched experience.
When I tell people now that I am a former competitive Halo player... that I had video game practices and plotted out strategies and captained an oddball team... it's a shock to them. I don't scan as a competitive gamer at all, and I play very little any more. But Bungie built those games, so they get the benefit of the doubt from me with Destiny.
Though I agree I am not blown away by what I have seen.