thats pretty stupid...
you only pay a higher rate on the income thats actually in that higher bracket...
ie: 10% on the first 10k, then 15% on whats over 10K
and don't forget to take out your standard deduction/personal exemption/itemized deductions which all come out before your determine your actual effective rate.
so if your raise would have put $500 in the 25% bracket, you only pay 25% on that $500, not your total earnings.
It wasn't really worth it. My check only went up by a few dollars, but the taxes that came out were more than 25%.