I started on Heroic and beat it in a day and a half I beat Legendary in a couple days about a month ago watch after the after credits thing for a little bonus video by the way! However, I feel the need to go back a lot and play through the campaign still because it was and still is that fun and interesting/challenging. I only need like 3 or 4 achievements until I get Security Armor and the Katana as well! I'm sad though I'm only a Major right now I haven't been playing a lot the past couple weeks because of all these exams and finals for the semester will be, added to our connection in this apartment sucks so I've lost 11 experience points because of router crapping out. Hopefully, I'll get to General by Christmas time.
Edit: Here's my stats friend me if you'd like to play sometime.
http://www.bungie.net/Stats/Halo3/De...er=LordSeth318