I've only read the first few posts and the last few posts. Here's my situation and decision.
I am engaged to be married. When we are married, we will not be in a financial situation where we can support a child, barring winning the lottery or God showering us with a surprising amount of undeserved grace in the form of the material/financial goods needed to support a child. We will both either still be in school or have just graduated and still have a lot of college loans. I have started charting my cycles so we can use NFP effectively when we are married.
Honestly, we would probably be able to support one single child right after marraige, one way or another, if we didn't use NFP. The child wouldn't have many toys, wouldn't have a large bedroom, wouldn't have a yard to play in - but it would have life. We would be up to our ears in debt, but what is that to the value of a child? Yet I still choose NFP, and claim that I will not be contracepting. Why? Because by delaying this first child, I provide for a future where I will be more likely to support more children.
If I have a child as soon as we marry, I will most likely not be able to get a job in my industry (software engineering). The initial delay due to my pregnancy will put me behind the industry right after college, and convincing someone to hire me at that point, in this economy, will be hard, not to mention take time away from my child. My husband-to-be has significantly less education than I, and will likely not be able to earn as much money as I will. His expected average income with his degree is probably about 20,000 - 30,000 dollars below mine. This means it will take us longer to pay off debts, especially with a little one to provide for. We will not be able to support a second child for years, possibly five or six. We will then barely be able to support ourselves for a while longer, and will likely have a period of years before our third child. We will be unable to tithe or donate money to others as well.
On the other hand, if I postpone pregnancy and work in industry for a few years, I will be able to pay off my college debt within a year, even if I earn 10,000 below the average income for someone out of college with the degree I will have (I go to an unusually good school, so I actually can hope to receive above the average a little). If we avoid unnecessary expenses such as a car (not necessary with the great bus system in this area) before we have children and focus on saving most of our money, we would be able to comfortably support a child in a year, look into starting the process of buying a house with enough space for a large family, buy a minivan for taking all of the kids to school and ball games (buses aren't as practical for large families), and still be able to support a second child very shortly thereafter (maybe immediately! and twins do run in my family . . .). Plus we will likely have more flexibility in our parenting options and be more likely to afford one of us staying home with the children full-time. A delay of two years could mean many more children in the long run.
How can this desire to ultimately have a larger family be called contraceptive? Worst case, my reasoning is faulty. Yet could one honestly say I have *grave* reason to use NFP, in the most extreme sense of the word grave? My life would not be in danger, nor would my child's. Yet I sincerely believe that postponing the first child does the greatest service to life. I hesitate to presume that God will provide no matter what, especially after seeing my own Catholic parents divorce (marraige was annulled) after seven children because my mother was diagnosed with schizophrenia, declared an unfit mother, and was not allowed to be in the same household as her children and seeing various other trials in my family arising from unplanned pregnancies. I believe it was St. Ignatius Loyola who said, "Pray as though everything depended on God, but work as though everything depended on you." Doesn't a similar sentiment apply to using prudence to determine whether life and God will ultimately be better served by having children now or delaying for a time?
Is NFP overused? Yes. Without a doubt, some people see it as Catholic bith control. This mentality is not good or healthy. But there are non-life threatening reasons to use it to space children, and I would imagine that finances are a common and very real reason for spacing children, even if finances are also a common excuse. Obviously, buying that third car probably isn't necessary, unless you have twenty children who won't fit into less than three cars

But wanting to be able to support additional children after this one seems to be a healthy reason to delay. And hey, if God really wants you to have children, there's always room for miracles with NFP - the uterus isn't made hostile to the child, or God's Will.
Also, NFP is different from ABC because it requires more sacrifice. You are saying, "God, I realize that I cannot make the sacrifice involved in giving myself to a child just yet, so I will sacrifice the pleasure of sexual union for a period of time to avoid this other inprudent sacrifice." Not the same thing as the ABC-user, who is saying (at best), "God, I realize that I cannot make the sacrifice involved in giving myself to a child just yet, so I will take this pill/use this piece of rubber/ insert this piece of metal inside me / etc. to make it more likely that when I enjoy sexual union with my spouse during the fertile period we will not conceive a child." I think that anyone can sense a fundamental difference between these two statements. A varient on the contracepting side that is different from the one stated before but is still common is this: "God, I don't want to deal with the difficulties of another child right now, so I'm going to contracept to make sure that I can have the pleasure of sex with my spouse during the fertile period as well as the infertile period without having to take on another child". This is even more obviously anti-life, or at least not pro-life.
This is my (very wordy) take on things.

God bless everyone, there have been some great posts on this thread. I'm going to go read some more of them.
-Ethel