Re: What DON'T you like about this phone.
I tried both the G2 and One, ended up returning the G2 and going back to the One.
As far as what I don't like about the One: Blinkfeed + Sense. they are just awful.
But Nova Launcher or Google Experience Launcher both work great on this phone and get rid of that problem, I still wish there was a way to disable Blinkfeed even though I never see it.
As far as comparing both phones:
The G2 had better battery, and better stock OS, but horrible sound quality for phone calls was bad, reception seemed worse also and the screen had very noticeable grid in the background.(part of the touchscreen technology I guess.)
The HTC One has a worse button layout and Blinkfeed/Sense. It also has a slower CPU but I actually think its smoother than my G2 was.
Overall the HTC One just felt much nicer and performed much nicer than the G2.