Hi Jenny,
Unfortunately it's very hard to give any real helpful info on insurance in a general sense because so much is dependent upon the employer who provides the coverage. They determine most of what's covered and what's not. However, to just sum up the differences between HMO/PPO/POS it's basically what Julie already said. HMO's require a primary care provider who will determine everything you are allowed to do medically (what drs you can and cannot see, what hospitals, etc...). If you have a great primary care provider who is willing to give you the referrals you need, it's not that big of a headache. I worked for BCBS for several years and therefore had that insurance. I had an HMO and my Primary care clinic would give me 4 referrals a year for the CF Center automatically to cover the 4 visits we usually made and if we needed more it was never a problem. Unfortunately many drs aren't that nice about it. Primary care providers do not usually like to give referrals unless they have to. With CF it's always a have-to case so most are fine with it.
PPO stands for Preferred Provider Organization and that basically speaks for itself. To be "in-network" you just have to see drs who are within the Preferred Provider Organization with your insurance company. Usually that is a great big list so it's not a problem. You don't need a primary care provider and can change drs every day if you want so long as the dr you choose is in that organization. And you usually have out of network benefits too, but you will pay much more of the cost. PPO's are great if the policy you have is a good one. Again, that depends on where you (or your spouse) work. Most PPO's have copays for dr visits and sometimes deductibles for hospital stays. They vary greatly though.
POS stands for Point of Service. POS is a cross between an HMO and a PPO. You have to choose a primary care provider and you have to get referrals, but there is a second level of benefits if you choose not to see your primary care provider. With an HMO you cannot go anywhere without a referral but with a POS you can, it's just that you will pay more out of pocket.
Insurance can be such an overwhelming part of life, especially for those of us who depend on it so much more than the average person. It's important for everyone but can be life or death for people in our situation. HMO's will almost always be less expensive because the insurance company is saving so much money that they lower the premiums. They have a set fee that they pay your primary care clinic and don't have to worry about you running around seeing all these different doctors and racking up bills so it's great for them. And as long as you have a primary care clinic who is willing to work with you, I'd say go for it. Just make sure of that up front. Otherwise it will be a huge headache for you. Ask the dr you want to choose as a primary care provider up front if he/she is willing to give you a referral for so many (however many you need) visits to your CF dr. Have that done beforehand to prevent problems. With an HMO you have absolutely NO coverage without a referral so that's very important.
Hope this helped a little...Best of luck to you!