Retirement is 1.7% x years of service. So 20 years gets you 34% retirement. It's based on your high three earning years.
I would say at this point the only people who should consider this job would be low time Helicopter only guys. The reality of the situation now is that if you have any fixed wing time you should go to ANY airline that will hire you. Over the course of your career you will have way better benefits and earn a boat load more money.
I know people like to complain on these message boards so you should always take all this info with a grain of salt. But I am in one of the better locations in Air and Marine and we have had 4 guys leave to go to other jobs in the last several weeks. There is a reason a high percentage of current Pilots are looking for better opportunities. None of us really know what this agency is going to look like in 5 years. At the current rate of decline we are seriously concerned about whether or not Air and Marine will survive in its current form for us to make it to retirement.
My opinion is that this isn't a terrible job but it used to be WAY better and its getting worse every day due to incompetent leadership and high attrition rate.