To people contemplating returning it, only to buy it again later...why? You're just costing yourself money. Say, on average, you spent $60, you get $40 on a trade-in (which is probably the highest you'll get) then re-buy later at say, $30. You spent $90 to get $40 in trade-in..? It's your choice, you can do what you want, just saying from a financial standpoint, it's kind of pointless, unless you just really need the money now to play a game that actually works right now.
But, this is Halo. It'll get fixed. I know nothing 343i is saying (or not saying) right now really reassures that notion, but this is not a franchise they can just leave DOA. With the backlash the Halo 5 MP is already getting, they have to protect the brand more than ever.
EDIT: Unless you get a full refund/full credit of course, then it makes complete sense.