[G2 Q&A, Help & Troubleshooting] Turbine1991:
Hey FedericoUY, I received my phone about a month ago and I'll go through my journey from all of the likely problems and what's required for unlocking, rooting, installing a rom for the first time on this device. I'll describe the benefits/disadvantages from the different rom distributors recommended for this device. Until a few days ago I would have agreed AOSP was better left avoided on this device, and why CM11 is still not recommended for the G2.

When I received my G2, while I had the intention to flash it. I was gravely disappointed with it, because of the shocking software and default setup. But it's become my favourite phone since. I too thought CM11 would do it for me, it really didn't on this phone. And the display & specs make it seem extremely outdated, not to mention none of the phone-specific features really worked.

(In order of events)

Sim Locking for AT&T (do first)

By default it's locked, as I imported it through the US and without an account for them I had to purchase a 3rd party unlock code for $2. Strangely I had to keep it unlocked on the stock firmware for a certain amount of time (tried a day) before it remembered the unlocking when flashing a custom firmware.

Rooting (do secondly)

The only method which worked on the latest G2 stock rom was to use "Stump Root" in the "Brute force" mode as the latest rom version didn't have a pre-configured rooting routing.

Installing a custom recovery (do third)

The only method which worked on the latest G2 stock rom was an app called "D800_AutoRec.apk" which just installed the latest TWRP recovery, from there I could flash anything.

Which roms are decent for the D800?

While personally I've stayed with more AOSP roms like CM and AOKP, the best rom & kernel to use in terms of performance/battery life and phone specific features is not the stock G2 software nor AOSP. I'll explain further why.

For the kernel, the arguably most matured and feature rich, battery friendly and performance suited kernel is the Dorimanx kernel. Which is unfortunately only compatible with stock G2 & G3 roms.

With this in consideration and all of the improvements in the G3 firmware, fully supporting this phone's features, makes the G3 roms peoples choice, in particular CloudyG3 targeted for the G2.

When it comes to AOSP like roms, there is two okay kernels which are compatible with CM and the other is only compatible with AOSP roms, with a few exceptions. Both of these kernels have poor battery life in comparison and produce a lot of heat, not to mention lesser abilities in terms of tweaking (overclocking, underclocking rate, faster charge, etc). It generally only gets worse from here using rom released kernels. It's fairly uncommon for features such as double tapping wake to work, and the lack of on-screen keyboard usability improvements.

However, Lollipop has turned things around. While not flossing as much battery life savings as CloudyG3 with the Dorimanx kernel, performance, design/look (can change Google keyboard to old theme) has brilliantly increased. It's been the only close to stock rom I've ever been largely happy with. Despite not having any real CM features and a few bugs at this moment in time.

Therefore, if you like the ability to tweak and charge faster and overclock a lot with great battery life I suggest CloudyG3 and Dorimanx. If you want an AOSP rom, I'd use Lollipop. If you want a full featured stock rom with a nice kernel, I'd wait awhile and opt for CloudyG3 until lollipop roms mature. For a battery comparison, the stock G3 rom with a custom kernel lasted me 5-7 days without charging, with CM11 I can only get about 1 day if I'm lucky.