You know... you are right in the sense that the G3's UI isn't as smooth or fluid as the M8's, or the Nexus 5s.... I'm with you on that. But in other areas, the G3 beats down both of those phones.... So you could say the same thing, but changing around the feature and phone. Would I pick having a buttery smooth UI if it meant I had to deal with the POS camera that's in the M8? Not in a million years.... With a few tweaks, I addressed most of the G3's UI kinks (which are a bit over-exaggerated in any case).... so I'm good.
Is the G3 perfect? No.... there isn't a perfect phone out there... but do I think that it's flaws are the least problematic of any other phone? But that's me. If I didn't have to use my camera for much, I'd have gone with an M8, etc... But the G3, for what I want out of a phone, was clearly the best one available and I'm happy I snagged one.
As an aside...what kind of bugs me a little is that all the ingredients are there for someone to put out a perfect phone... Give me the M8's sound, the G3's camera and form factor (might not work with the earlier item, but go with it heh), the Nexus's software and OS support, the Z3's battery and maybe, dunno.. the Note 4's screen to get everyone involved. But every phone on the market right now has something about that that kind of tempers things a bit. Now, if the Nexus 6 has a good camera, that might be as close as any, but I'm not holding my breath on that... I'm guessing it's going to be mediocre.