It definitely is not something that everyone needs. My view on adapters is this.
If you're going to buy an adapter, you should get a good one, not one of those cheapy ones. I think the footage that comes from them generally looks like crap and doesn't accomplish anything. You'd be way better off shooting with the stock camera. This is my opinion though, many people use the cheaper adapters and they fit their needs, just don't expect incredible looking footage from them. You get what you pay for. I personally think the money spent on an adapter could be spent much more wisely elsewhere. Adapters are over rated, but they do have their place and time.
If you just want to get one to play around and have fun with, try making one or just go for the cheaper adapter. Just don't expect it to hold up to a Letus, Redrock, shoot 35, etc.