No, the benefits are not good. They are better than municipal jobs, but rarely stack up to academic positions or private consulting -- at least in my field. The union you would be a member of would determine vesting, years in service and retirement age. If you were an academic in Massachusetts, you may be able to "buy back" years of creditable service. Salary increase are slow (low), but steady. Look at the salary cap in the position to see if you could live with that.

Any position Assistant Director and above are generally non-union. The health insurance is expensive but comprehensive.