I am currently experiencing some bad luck with the Double XP Bonus feature in MW3. If you redeem codes on DewXP.com and apply Double XP minutes to your gamer ID then a golden double XP icon appears in your barracks screen and shows you how much time you have in Double XP.
Frustration was experienced when I went to redeem 30 minutes of codes tonight. The instructions state to redeem your codes then apply them to your gamer ID then login to see if your minutes have registered and you can see the golden double XP icon. But once you start the process of applying them to your gamer ID there is some tiny text online that states you must be currently logged into MW3 multiplayer mode while you are applying the minutes. If you are not logged in then MW3 won’t register the minutes but DewXP.com does subtract those minutes from your 24 hour double XP time limit imposed to each individual gamer ID. Therefore I logger into MW3 mulitplayer and then went online and logged into DewXP.com and went to enter a couple codes. Then I applied them to my gamer ID. Only after I looked at my television did I see that inactivity has cause MW3 to revert back to the welcome screen. Therefore my 30 minutes did not go into MW3 but were take from my available 24 hours. So I lost them. I wish this process was easier to navigate.
Update (11/15/11): Today when I logged in the 30 minutes were indicated on the barracks screen.