Having used the iPhone 6 for almost three weeks now, I'd say the review is very much on the mark.
It's not so much any one thing as just a lot of tangible upgrades that make it nicer to use than a lot of phones I've tried (and I've used a large chunk of newer Android devices). The screen is more of a "finally" feature, but it matters. The battery life is genuinely good enough to get through a *real* full day of use involving Twitter, Instagram and the like. And importantly, this is probably one of the most dependably good camera phones I've used. Unless you're in a very obviously difficult shooting situation, you'll get quick focusing, sharp pictures and rich colors.
A lot of existing Android and Windows alternatives seem to have an Achilles' heel in their cameras, where seemingly superior specs fall apart in real life. High-end Nokias like the Lumia 1020, 1520 and Icon all have super-high resolutions and great camera controls... but they're slow as molasses, and occasionally freak out with wildly inaccurate color balance. Samsung Galaxy S5? Good shots in the daylight, but it's terrible in low light and still suffers from the "Samsung twitch" (i.e. it blurs if you so much as give it a funny look). The LG G3 produces drab colors, the HTC One M8 has both a low resolution and overexposure issues... and so on. The iPhone 6 just doesn't seem to have those pitfalls -- even if you demand manual control, it's now easy to get through third-party apps.