Most the reports were from phones with 5xx serial numbers ie those made in 2015. There's very few reports of bootlooping from the 6xx models. My 509 numbered one bootlooped within 3 months and was replaced with a 603 one and has been no trouble at all since. I get about 1.5 days battery life from it with low usage (mainly checking messages, fb and a bit of browsing) so got a spare battery right awhile ago and it's much lighter than carrying around a powerpack. Only annoyances are because of the curved back it rocks a bit if you use it lying flat on a surface
In use it's a lovely phone. Great screen and camera that lets you shoot RAW. Gets a bit hot if you shoot 4K video but otherwise video quality is very good as well. LG have just announced it will be upgraded to Nougat later this year. My photos are saved on the sd card and contacts backed up on google and the card so even if it did loop again, there isn't anything to lose
If you can get it new with a 24 month warranty I wouldn't be bothered at all if you can get it at a good price. LG will repair it directly if you bought it new and at this late stage will probably replace it with a G5 or G6 if you get lucky in 20 month time!