Glad (at least in a "I'm not crazy" sort of way) to see others having issues with WiFi. I have an iPhone 6 and an iPhone 5. The 6 has no problems connecting or staying connected to my home network, fortunately. It's outside networks that are giving it fits. I am sitting in Best Buy as I type this and I FINALLY got my 6 to connect to the store's WiFi; my 5, about 6 inches away, had no issues connecting. my iPhone 5 is updated to 8.0.2; the 6 is not.
Although all software/hardware has issues following its initial release, Apple has been a bit sloppier recently than we're used to. Yes, the company is busy releasing products and updates but it also has thousands of employees commensurate with its level of activity. I hate to use the old Steve Jobs cliche but somebody needs to be a perfectionist here or at least inject a higher level of scrutiny given the increased spotlight on Apple and its products.
I also will say that, generally speaking, resetting the device as a new phone might solve some of the issues I see posted. As the iPhone is really a computer, they all need a little refresh every now and again even though the Apple propaganda machine leads you to believe otherwise (i.e., it just works). According to many of the genius at the stores, they restore their phones monthly. That's probably overkill, but quarterly or when installing a major update is probably necessary.