It's still not an easy process to downgrade your HTC EVO 3D with HBOOT 1.50 S-ON to 1.40, which allows you to achieve S-OFF and beat the absurd security that prevents you from using recovery normally to flash radios and kernels, but it's getting easier thanks to the work of Closeone.
Closeone has put together a bootable live CD containing most of the tools you'll need, along with helpful links to guides that will enable you to do things such as boot the CD from USB.
While it's not a one-click method and a computer and linux terminal are still involved, the commands are mostly done for you via scripts.
It's still a very uncomfortable process involving bricking your EVO 3D in order to get it into the right EMMC recovery mode, and then using EMMC recovery tools to push a signed, older bootloader into the corrupted area. But now there's a one-stop thread for everything you need to do it.
Personally, I'm still going to wait a little longer until this thing is completely wrinkle and burp free. I recommend that you do the same.
It's still wickedly awesome to see progress being made toward this being available to the masses of locked S-ON people.[xda-developers]