Discussion: Gross.

I just wouldn't eat.

It's not ideal. The chocolate milk overpowers the taste of the cereal, especially if you've got something more subtle or multi-flavored like Honey Bunches of Oats, or anything with fruit. Then it just tastes like you're eating chocolate milk with chunks of stuff in it.

Perhaps chocomilk would be appropriate with either a chocolate cereal or something suitably bland and flavorless, like shredded wheat.