The best thing about the Neutron Star is it's cheap. It's fantastic if you are short of cash. They might be slow and a bit obsolete, but great against pirate fleets. Mark II adds hangars, Mark III adds trubolasers, and the later variants... kepp getting better, (quads go to sextuple lasers)
It's a great second line cruiser. Against anything imperial and modern - they die. They do have 1 weakness - short range fire. They are vulnerable to anything with a decent range, such as Carrack-Class.
Overall, great ship - really useful. It may not be the best militarily, but economically, it's a winner.