I don't know what other places in the area pay but I only took a small pay cut when I moved here. Once you factor in the cost of living that pay cut works out to be a decent raise.
I get the impression that IBM will start using more Red Hat tech, but for the most part we are keeping the two companies pretty separate.
Median hourly wage, Computer and Mathematical Occupations, Durham-Chapel Hill: $42.77 ($85,540 ann.)
I just ran the numbers for a $100k salary in NC and $130k in California. The person in NC will pay $17203.92 in federal taxes and $5250 in state taxes for a total of $22453.92. The person in California pays $24403.92 and $9094.69 for a total of $33498.61. This brings their post tax income to $96501.39 for California and $77546.08 for NC. The person in California only makes about $1.5k extra a month.
There are plenty of non-monetary reasons why someone might choose to live in one state or the other but you do need a lot more money in California to cover the cost of basics like housing. Not properly accounting for that could give someone quite a shock if they relocate there.
Fewer hot (HOT! HOT! HOT!) tech jobs? Probably.
Furthermore, Charlotte is heavily banking and finance, and thus lean heavily on H1B visas for most of their enterprise jobs. I've had recruiters contact me for jobs in the area and the salaries were a joke. Honestly, I don't know if they were for real or just using it as 'proof' that they couldn't hire any Americans so they could forward off a few hundred more H1B petitions to USCIS...