IBM said "same pay for a year" but it turned out to not quite be true.
At IBM
Your bonus is lower, they are making an extra cash payment as a retention bonus to make up most (but not all) of the difference.
Your 401k matching is lower (if you landed in GTS). They will add an extra 3% at the end of the year in the 1st year only.
401k matching is only paid once at the end of the year, so beyond the lower matching you are losing compounding interest for the year. Oh, and don't quit before the end of the year of you don't get it.
Health insurance is SIGNIFICANTLY more expensive for and is less widely accepted. We were promised quarterly payments to make up the difference. Except those quarterly payments do not even cover half of the difference for most people AND they are taxed without being grossed up, so you get maybe 1/3 of the difference. Some people won't even get the quarterly payments because they have no dependents but their insurance can still be up to 3x more expensive than what they had under AT&T.