It's a personal decision that I think depends on how confident you feel about matching, weighed against your desire to attend the program offering the prematch. There are no general guidelines regarding who should accept a prematch offer.
If you think you are a very weak applicant, and you're worried about matching, then I would take it, assuming it's in the specialty you are applying for. I would be hesitant to take a prematch in family med if I really wanted psych.
If you would be happy going to the program offering the prematch, then of course take it.