To me, the iPhone 6 is an underwhelming, overpriced phone with a huge advantage: iOS. iOS users are locked into Apple's ecosystem, in the same way Android users are locked into Google's ecosystem. When you buy an iPhone you aren't buying a phone per se, but rather a key to Apple's services.
The iPhone 6 Plus is a step in the right direction with its 1080p display, but is crippled by its horrible internals. Dual-core processor? 1GB RAM? This isn't 2012, Apple. But I have no doubt that it'll deliver decent performance, as Apple has control over both hardware and software and is extremely competent with software.
Let's talk about the software: iOS 8 is excellent. It's optimized for the hardware, has great memory management, and is very pretty. The Appstore has a huge variety of apps from top developers and independent publishers, most with consistent design philosophies and usage paradigms. This is possible because of Apple's strict guidelines for Appstore submissions, which presents both iOS' greatest strength and biggest weakness. The lack of freedom results in reduced functionality in certain apps and can cause problems when trying to find an app that does something like file management. However, most users don't need this and the problem becomes a nonissue with a simple Jailbreak.
Bottom line: If you've heard of an app, it's probably available on iOS. That is huge.
The biggest problem with any iOS device is aging. If you've owned an iOS device for more than a year and a half you'll notice a huge drop in performance from when you first bought it. Uninstalling apps and killing apps that might be hogging CPU cycles doesn't help either; you have to either deal with the lag and bugginess or buy a new device.
In conclusion:
Would I buy one? No, I am locked into Google's ecosystem (I've invested somewhere around $2000 in it). Should you? If you're already in Apple's ecosystem and due for an upgrade, absolutely. If you're new to smartphones or aren't really invested in any mobile OS, go ahead and try it out along with Android, Windows Phone (soon to be just "Windows"), or maybe even BlackBerry and then weigh your options.
And watches? Not sold on their usefulness. I might get a Moto 360 or something to test this, but I'm more interested in Google Glass.