That's absolutely right. You can switch job any number of times during OPT, only thing is that you have to notify your international program office (DSO) every time you do. During switching job you get 10 days or so grace period which also does not counts towards the 90 days period (please confirm this from an official source.) Also just for the records, the 90 days unemployment period is not only at the beginning of the opt start, it's 90 days at any interval of time in between that 12 months. Just want to make it clear that after spending your 60 days you get a job and then later you switch to another company does not means you have more 90 days, you have your 30 days left :).

thanks,