Assuming your pay is the same, your take home will be different on your next check.
The Bush Tax Cuts have been extended. So the federal rates stay the same. But the making work pay credit has been taken away so the net federal tax payable will increase.
Federal tax withholding tables have gone up and you will have a bigger deduction on your pay check.
The SS deduction has gone from 6.2% to 4.2% for the employee.
You will have 2% less of a deduction for SS.
In most cases the gain in SS will be bigger than the loss in fed withholding and your net pay check will be bigger this year.
The change for the Fed rates is good for two years and the change in SS is good for one year.
So in 2012 your pay check will be smaller than your check in 2010 all else being equal.
2013 is set for taxes going up further and we will watch a fun 2012 campaign that tries to address this.
Happy New Year and enjoy your stimulus.