At my older son's college, registration priority is given to those with the most credits. Taking CLEP tests has enabled him to register before many of his peers because he has passed the next credit-threshhold for registering.
I'm considering having my younger son CLEP as many tests as possible, even though they aren't needed for his major, just so he can register a few days ahead of his peers. He already has 12 college credits through AP and CLEP, so he'd need to take only 6 more CLEP tests to reach the 30 credit threshold. There are CLEPs for many of the courses he's taking this year in high school, so it wouldn't be onerous. The college he plans to attend takes CLEP, and although he wouldn't need all the CLEPs toward his degree (engineering), it would help in earlier registration.
Fortunately, CLEP and AP exams don't count toward the 140 credit maximum our state has. (Students have to pay a tuition premium for more than 140 credits.)