I tried out everything on my m8. Recently gained s-off and went flash crazy. But I found Captain Throwback's GPE port for Sprint m8. First time ever....end of the road. http://forum.xda-developers.com/show...762336&page=68
The battery life from this thing is beyond imagination. Buttery smooth. I do not even want to try anything else. If I was on another carrier Google Play Edition would be the purchase. Did not do the "conversion". It is a flashable ported ROM. Solid, stable. Customization through the Xposed framework is flawless.
I tried ARHD, it was aiight but seemed less glossy than the stock ROM. I will say Sense is kinda awesome. The battery on stock is very good. Also tried insertCoin. Did not like it. Battery took a hit. Renovate is excellent. Viper is Viper just a new flavor, but seems to not be the destination for HTC devices that I remember. Viper was the shit, BITD. Bad Boyz was not great, either.
Of the Sense ROMs Renovate and ARHD were my favorites, with Renovate by far being stand out.
AOSP is wacky. Lots of whack shit. CM is the worst CM on a device I have ever used. You have to tinker with data pretty much on all builds. The AOKP that is based on OmniROM is solid. It is hard to find actual Omni builds for this device, but the source is there. Dirty Unicorns is based on it and it is amazing.
These ROMs do not even compare to GPE, tho. I didn't even think I would like GPE but yes.