[Nexus 6 Android Development] Syndrome666:
Having flashed quite a variety of different builds of various Nougat custom ROMs (both official and unofficial builds) on my Shamu, I can chime in from my experience. CM based ROMS have the more desirable features but more bugs like apps freezing or crashing, probably due to CM itself still being buggy. AOSP based ROMS seem to run cleaner, by that I mean, there's less crashes and freezes, better overall stability, and I tend to hang on to these ROMS much longer. So far, I've tested DU 7.0 alpha build 1 and 2 (stock kernel), Cyanide 7.1 build 11/19 (stock kernel), a few random Nitrogen 7.0 and 7.1.1 builds (stock kernel), SiX ROM 7.1.1 with stock Open Gapps on both build 3.5 and 3.8 (Flash kernel 1.6 and 1.8), Pure Nexus 7.1.1 (Flash kernel 1.8).

I've used only dev recommended gapps on the ROMS where Gapps aren't mentioned (if Banks Dynamic, I tend to go with Full Gapps package), where devs left it up to the user, I tend to install open Gapps stock, SiX ROM v3.8 recommend banks dynamic mini, and indeed using open Gapps stock on this version caused play store sign in issues, couldn't stay signed in, so I scrapped the ROM and switched to crDroid 7.1.1 with open Gapps stock package and left the kernel stock. Couldn't restore my setup, so set it up manually, had lots of app crashes and freezes with chrome, titanium backup, and ES file explorer. Bluetooth pairing in my car wouldn't display track info. After reboot it completely failed to pair. Otherwise the ROM runs smoothly, oh and battery life is poor like cyanide ROM.

So back to the original feedback, of all these tested ROMS, I found Pure Nexus and SIX Roms to have a consistently awesome battery life with 5-8 hours SOT. DU came in second place with similar SOT, but not consistent throughout each build, I'm sure they've sorted or will sort this issue out. Their very first public alpha build for Android 7.0 gave me amazing battery life with amazing stability but laggy animations with stutters. Cyanide was the best Nougat ROM I've used as far as smoothness, stability, and features go, but the battery life didn't live up to my liking, with 2-4 hrs SOT per charge. Nitrogen is somewhere in the middle with about 3-5 hours SOT per charge and some minor bugs. crDroid 7.1.1 is a very smooth, yet buggy ROM with similar battery life to Cyanide 7.1

Overall I'd say SIX ROM by Frankie T is as close as you'll get to stability, smoothness, excellent battery life, no app or UI crashes. Pure Nexus gave me almost the same experience, but with 1 noticeable bug. Sometimes notifications wouldn't dismiss requiring to either clear the respective app cache or perform a system reboot. I honestly don't know what Frankie did to pure Nexus but he must be a perfectionist, because no other nougat ROM I've tested had this good of a balance, well pure Nexus and some DU builds are up there for their battery life and stability, but for additional features and further stability, SIX ROM is top notch, even supports OMS which I'm not a huge fan of, but it's there if that's your thing.

With that said, I'm off to flash one of the RR Nougat 7.1 builds with Blackbird kernel and probably a mini banks dynamics Gapps to stay on the safe side, since most CM based ROMS don't seem to play well with open Gapps or full/stock packages. I just like to test and see which ROMS have okay google feature working, so far most seem to break except crDroid 7.1.1. as buggy as crDroid is, it's also very smooth and the okay google feature just works. There's plenty to like and dislike about each ROM I've tested. I'd say cyanide would be my daily driver had it not been for its poor battery life, although I've heard that the 7.0 builds of that ROM and many others had better battery life. 7.1 and 7.1.1 seems to be problematic on the battery side of things for most Roms. So if you're looking for best battery life on Nougat ROM, try pure Nexus, SiX, possibly sky dragon, and Roms based on stock google or aosp Android.

So in conclusion, if features are your priority but stability and/or battery life don't matter, then CM based ROMS all the way. If you want battery life and stability but don't really care about features too much, aosp base is your ticket. There's really no perfect ROM that captures everything, bit of the ones I've tested, SIX was my favorite of the AOSP base, Cyanide from CM base. Cyanide has a black theme plus just about anything you'd like to color code/theme manually and comes with black and blue themed aosp apps, maybe some further tweaks to the kernel or CPU would get you a better battery life, I just didn't have the time to test it that in depth, but I managed to hold on to it for two whole weeks just because it's that good even though the battery got me to early evening at best. SIX ROM lacks most of these features, but I was able to run it for two days on one charge with about 3-4 hits SOT per day. Pure Nexus will get you similar battery life to SIX ROM, but it's missing smart navigation buttons and no pulse equalizer plus a minor bug or two possibly. Okay going to download RR 5.8 and flash it with bb kernel, I'll report back tomorrow with my results, hopefully it won't force encrypt like it unexpectedly did on my first trial a couple weeks back, I'll throw in a fed patcher for good measure this time, although bb kernel should technically disable force encryption.