[One (M7) Q&A, Help & Troubleshooting] phairoh:
I completed my install of this fantastic mod yesterday and everything seems to be working flawlessly. Thanks so much for the great work! Since I can't post in the main thread I wanted to share my experience here as I ran in to a number of hurdles along the way.

tl;dr:

Started with rooted but stock encrypted HTC One m7 Developer edition (US Version) with S-ON and old version of TWRP.

Ended with MaximusHD 50.0.0, S-OFF, unsigned 7.15.401.1 firmware, and everything seems to be working perfectly.

***Disclaimer***

If you follow any of this advice please be sure you back up first.

/***Disclaimer***

I began yesterday with stock but rooted HTC One m7 Developer Edition (US version) with S-ON that had an old version of TWRP installed. I had installed it months ago when I originally rooted the device and had intended to install ROMs and/or mods and simply never got around to it. Since that time I had encrypted the device using the built in encryption in Kit Kat.

My original plan for my device was to restore it to as close to stock as possible so that I could finally install the OTA system update that had been bugging me to do so for weeks. After trying to follow many of the guides to do that I finally determined that the only way I could ever achieve this goal was by getting S-OFF.

Because I could not turn off my lock screen (due to the device being encrypted) I determined that the only way I could get S-OFF was by using Sunshine (I don't know the rules for external links on this board, so just google: Sunshine HTC one). It costs $25 but worked perfectly for me so I was happy to pay. YMMV!

So now I had a rooted and S-OFF but encrypted device and I figured instead of going to stock I might as well see what else I could do! Googling: HTC Lollipop lead me to the new MaximusHD release and I figured sure!

First thing I had to do was get the newer version of TWRP on my device. I began by trying to use the TWRP Manager in the play store but for some reason I could not get that to work properly (my guess is that it was somehow due to the encryption, as that has been a hurdle on a number of other steps). I decided to use the Fastboot Method and that worked great, but then after starting up TWRP it was asking me for my encryption password. Although I know for certain that I was typing in my correct password TWRP never accepted it and when I loaded in to TWRP after hitting cancel it obviously could not see any of my device's storage. In order to overcome this I did a wipe and a factory reset from within TWRP which while although it cleared all my data it also got rid of the encryption. I then rebooted the device, ran through the stock setup stuff, turned on USB debugging, and copied over the MaximusHD zip to /sdcard/ROMs/ (a folder I made) using adb push.

I then went in to TWRP and did a wipe. This unfortunately deleted my MaximusHD zip file! I'm still unsure exactly what location on the sdcard is safe from a wipe (I assume /sdcard, but I'm not sure) but fortunately adb push still worked from within TWRP (albeit much more slowly) so I copied over the zip again. When that was complete, I did the install and followed the onscreen instructions, rebooted, (the first boot took a very long time [maybe 20 minutes or more] so be patient) did the setup stuff and now I had Lollipop!

But I still wanted to flash the firmware. Ultimately I followed this guide for flashing the firmware. I did have to change my cid to 11111111 but after that the flash worked as expected. Upon rebooting I immediately noticed increased responsiveness of the system and while I have very limited data my battery performance also seems to be significantly improved.

That's my story! Hopefully it helps someone somewhere.