it's qualitative. to help guide you in determining how good it is, take a look at how many competitive specialties people match in.
if i had to group them by competitiveness:
higher~dermatology, orthopaedic surgery, neurosurgery, otolaryngology-head and neck surgery (ENT), opthamology, radiology, urology
a bit lower~ radiation oncology, internal medicine, emergency medicine, pediatrics, physical medicine and rehabilitation, anesthesiology, neurology, pathology
even a bit lower~ ob.gyn, family medicine, psychiatry.
these are just rough placements, sorry if i offend a particular speciality.
also, it's important to weigh the institution that the person matches in. for example, an internal medicine match at Mass General is going to be more competitive than an (no-name-institution but "harder" specialty)