1. Resets all of your custom options for the "host" player. Sensitivity, control scheme, the whole bit.
2. Makes your emblem this weird clover thing. It goes away after you dashboard, but it's still annoying.
3. Two people can't edit their options (which is necessary because of #1) at the same time, despite having two separate start screens.
4. My connection took a noticeable dip while playing splitscreen.
5. Frame-rate dropped HEAVILY. A little bit is understandable, but this was excessive...
Treyarch needs to take a page from Bungie on this... these shouldn't be that hard to fix.