I got the G3 a few days ago too. I was chosing between M8 and G3, but opted for the G3. The metal design of the M8 is extremely nice, but the G3's "fake metal" along with its curved back makes it both good looking and nice to hold. Also, the M8 bezel was quite off-putting. The (almost non-existant) bezels on the G3 together with the screen - 0.5" more in basically the same form factor - makes it a winner imo. I came from a 4.7", so I was afraid it would feel too big, but it sure didn't. Form factor is great, you get used to it very quick and it doesn't feel large or cumbersome.
I love Sense on the HTC, but honestly, LG's software isn't bad. Maybe a tad less responsive, but not annoyingly so. It feels snappy, menus / settings / built-in apps work well and look good. I actually swapped launcher (to Nova), and it felt faster than the standard launcher. Not sure if that's the case, but overall I'm happy with the speed.
The camera is fantastic, one of the better mobile cameras out there, and definitely better than the HTC. The camera app isn't all that great perhaps, but the quality of the shots are. Big pro for the LG here.
Battery life is good. Maybe not great (5-6 hours screentime, and good standby), but it's up there with most 2014 phones. No complaints. What IS good on the other hand is the wireless charging and exchangeable battery. Great to have. Also, the back is easy to take off, which means you can change it if it gets scratched, or get a new color and pop it on in seconds without needing a case.
The only downside so far has been that my shortcut buttons (quick start camera and such) tend to activate when I have the phone in my pocket. After turning that feature off it has worked much better, but I kind of miss the shortcuts. Also, it's nice that you can place widgets on the lockscreen, but why on earth only one widget per page? If you add, say, a 2x1 widget, and then another 2x1 widget, they get a separate page each that you have to swipe between to see. Not a great solution. Also, the NFC-icon stays on constantly in the notification bar when NFC is on. Somewhat annoying.
Anyway, the annoyances are very minor stuff. Overall it's a great looking device with awesome screen and camera. Couldn't be happier, and now when I had it for a few days I played more with an M8, and now I'm positive I made the right decision. Can't recommend the phone enough.