This is good question. For me, since I haven't really put any money into armor or maps and such, I wouldn't mind a completely fresh start. I haven't even been motivated to really complete the tougher achievements, so maybe a fresh start would motivate me to do that. Leveling up is the easy part, so that doesn't bother me.
I don't think I would be particularly bothered either way, honestly. The only thing that would annoy me would be listening to Halo fans complain, but you can't please everyone so that can't really be avoided.