When I was a grad student in Materials Science, I had a number of discussions with a variety of people in both academia and industry regarding the value of obtaining an M.S. versus a Ph.D. There were two general points of view that I found I could divide their responses into. The academic group all believed that the Ph.D. was worth pursuing. I believe that this was the case because they each had one. The group of people outside of academia generally all believed that getting the Ph.D. was not worthwhile. I think thhis was the case because none of them had one, and they couldn't see the point in spending all of that time and money pursuing something so specific.
In the end the M.S. is definitely worth obtaining because it will make you stand out from the rest of the hiring pool, and it will provide you with a substantial increase in salary over someone with just a B.S. degree. Unless you are certain that you want to pursue a career in pure research or want to teach at the college level, the Ph.D. is probably not worth earning. I have a Ph.D., and the comment that I hear more than 90% of the time from potential employers is, "You're overqualified for the job". The Ph.D. will close many more doors than it will open, so you will have far fewer job opportunities than you will have with a Masters. It will also not increase your earning power very much over a Masters Degree, and unless you have some contacts that can get you in the door with your Ph.D., you'll end up like a starving artist wondering where you went wrong.
Fortunately, I hope to teach at the college level on a full time basis at some point in my career. But finding that job is difficult too because of Affirmative Action policies. And if you plan on getting a research position in an academic setting, you will likely run into that problem as well. Good luck.
maui