Opus 17 already said this, but I want to emphasize it: Even if you let the ex claim the child, you still get to Claim EIC, dependent care credit and Head of Household (if you otherwise qualify) based on that child.
If you decide to go that way, it's good idea to let the other parent know that you will be claiming those items, as many first time separated parents are not aware of this rule and may try to claim those items, which will cause the IRS to send out letters.
