I have used Interjet a couple times to fly around mexico. While the airline itself is fine, their website and phone service are HORRIBLE. I am absolutely not exaggerating, and i have a witness, i once spent EIGHT hours, that is LITERALLY EIGHT HOURS on the phone trying to sort out a messed up ticket.
Fortunately, i was at a friends house in playa del carmen by her pool...but still, it sucked.
Having said that, any options that are cheaper and more convenient...i'm all about it.
ALso, TACA airlines is MAGICAL to fly on...