I don't think that this phone is necessarily a threat to the iPhone.
First, we don't really know how either phone works, b/c neither has been released to the market.
Second, a phone with no buttons is only as good as its touch screen technology. Apple invented a new technology, Multi-Touch, which (if Jobs is to be believed) "works like magic." I doubt that the M8 uses anything but existing, ineffective, "off the shelf" technology.
Third, and finally, the draw for many customers (like me) is that iPhone will sync easily and seamlessly w/ the Mac, including Address Book, Safari bookmarks, iTunes library, iPhoto library, notes/stickies, iCal, Mail. Imagine how much effort it will take to get anything like that kind of integration b/t a Mac and the M8, or even between a run-of-the-mill PC and the M8.
It's not about the raw specs, its about the user experience the gadget provides. With Apple behind it, you can be sure that the iPhone will "just work," both from a hardware standpoint (multitouch) and from a software/integration standpoint.
You can't be so sure about the M8.
Meizu M8 vs. Apple iPhone