My roommate has it and we play it all the time. One time on a team slayer game at Snowbound he killed the entire team with 1 grenade, it was called an "Extermination" and thanks to the sweet new replay feature we got to watch it over and over again.
Also another time on High Grounds, team slayer, he had the spartan laser and he fired at a Ghost and somehow got a double kill.. We watched the replay to see what happened and it turns out there was an invisible guy with a rocket launcher in mid-jump, ready to kill someone and he lasered him on accident, freaking hilarious...
I have to say, its pretty good, I played through the campaign with my friend, I wasnt really impressed, but from what I have heard they have a pretty good multiplayer 8/10 lol, I would rather play some select sweet flash games XD
halo 3 on heroic is what halo was meant to be, its the perfect setting for just the righ amount of action without the annoyance of legendary.
One time on high ground i grabbed the spartan laser and spent helf of the match sniping people with it while they tried to get to me lol
Another time me and couple of friends were playing sand trap on forge. I spawned a couple of hornets and after a while i turned into spark, snuck up on a hornet in flight, turned back into normal and boarded it, kicking the guy out and to his death, then shooting them as they tried to do the same to me ... hilarious