Seeing as none of us have actually lived under a one-world government, none of us can say for certain whether it will be a negative or possitive experience for humanity. If you were to ask a baha'i, they would be rather enthusiastic about the idea as they believe it's inevitable, and will mark a new era in human civilization. Then of course there's the whole 2012 thing where so many religions believe that area of time will mark some massive change, but I don't adhere to prophetic calenders personally.

I don't see how it would even be near to possible right now though, seeing as we have such wildly different values and such wide-spread ignorance; rebellions and new nationalities would be inevitable I think. And maybe that's why a world government would be plausible when we're ready, because if humanity actually transcended greed, ignorance, hate, and religious fanaticism, the world government could actually be a viable solution. As humanity lies now.... eh, we've got plenty of wars, poverty, disease, corporate greed, and overal suffering to look forward to.