Been using it for 2 years with no incident. Some people don't pull out when they know they're not in their fertile period, but we use it every time. I think it's obviously possible, but if you and your partner are extremely careful it can be a useful tool. However, I wouldn't use it exclusively if you're not 100% ok with an "oopsie".
Wtbmummy: If your OH is really making those kinds of excuses then I'd stick to condoms unless you're ready to conceive.