LG G6 vs G5, G4: should I upgrade?

The LG G6 is out and it's definitely a drool-worthy piece of hardware. Amazing screen-to-body ratio, beautiful design, and a lot of time spent on fine-tuning its operation and performance, as per LG's own word. Surely, there are LG device owners out there right now, spending more time than one would consider reasonable staring at pictures of the new phone and then beaming over to their own G5. There's that burning question:

Should I upgrade to the LG G6?
There are always a few things to consider when buying a new phone — is your model obsolete, does the new device offer more than just ...