For a given value of user-replaceable battery
Having looked at the guide, it's easily within my capabilities or I suspect 99% of Reg readers - no more challenging than replacing the battery in a non-waterproof tablet for anybody that's tried that. But it's still not something most people are going to want to do - they'll need a T3 torx driver, a pick, a spudger, have to remove the casing without splitting it at the very vulnerable points around the speaker, and the sockets, to be comfortable peeling tape and battery adhesives and then refixing them, and then hoping that they can still find the sixteen screws.
Interestingly, this does look like it meets the forthcoming EU regulations for user-replaceable batteries. Yet, given the harsh life that many mobiles endure, and the declining prevalence of basic mechanical skills and aptitude, I'm can't see many people splashing £200 smackers on a phone, and then replacing the battery after three years, and for those who would, they'd have had it done anyway by the multitude of mobile phone repair shops. I also wonder if the EU have properly thought through the consequences of encouraging the unskilled to play around fitting and disposing of naked lithium batteries? I wouldn't trust the public to even buy a safe replacement battery, never mind fit one.