I have been on this rom for a few days, so I may as well share my experience.
I'm using the build from 1-14 with OpenGapps nano from the same day. I installed using TWRP 2.7.0.5.EXT4. I'm using the MDK non-hlos with the OF1 modem. The rom I was on previously was Pheonix.V11.
Installation and initial setup was as easy as expected. Restoring backups from tibu was painless. 4g/3g, wifi, and gps (except the compass) have been working as expected.
I use hangouts for sms and mms messages seem to work, slowly.
Some apps (root explorer and waze to name a couple) seem to crash due to permissions issues, but the apps I use on a daily basis seem to all be fine, fortunately.
The speed and battery usage of the rom has been excellent. Both seem noticeably improved from my previous rom, but I don't have any numerical data to back this up. Also, I have not had any lockups or any issues requiring a reboot.
Besides the permissions issues affecting some apps, the biggest reason to stay away from Marshmallow roms would be the known issue with SuperSU (See the CM12.1 thread in original dev). If you need SuperSU for xposed or anything else, then this rom probably won't fit the bill. The built in super user worked for me in tibu and the power menu app I use which is all I needed.
I would say, that anyone curious about Marshmallow should at least consider making a nandroid backup of their working setup and giving it a shot. I know that my requirements are extremely simple compared to most, so take this with a grain of salt, but I will be using this rom as my daily from now on. :good: