It's pretty much the same as every other single thing in the airline industry:

If airlines oppose it, then it's generally a good thing for pax (example: tarmac rule, DOT compensation increases) ^

If airlines are for something, it generally screws over pax (example: baggage and every other punitive fee)

So, I usually go opposite to every 'want' the airlines have, and in this way I am all for the Google/ITA deal. I know why Google wants ITA and it will be excellent for pax and comparing the competition (basically take Kayak and expand the potential and search power x10).