Thanks for trying out the demo, and for the kind words. The feedback is much appreciated. In response to your questions/points
1. Unfortunately, horizontal head motion is fraught with its own issues; primarily if you read horizontal motion as forward vector motion - you'll be moved around inadvertantly when you're just looking around (with the movement active). It's what I started with, but moved away on, because it just didn't feel good.
There are a lot of options that can be tweaked to adjust the movement more to your liking... if it's the case that you don't move your head much, and thus keep falling below the activation threshold, in the version I'm working on right now (nearly done; just a bunch of UI work to update) I've removed the activation threshold... it just comes at the cost of rejecting some inadvertant head motion when turning your head - but it's fairly minimal, and I think ultimately improves the outcome.
I think the other thing I can do to improve the walking situation is to give an explicit walking video demo to show exactly the extent to which you need to walk/move on the spot to provide a good outcome. In my live demos, the instruction 'walk on the spot/in place' seemed to be insufficient for some people (while others understood right off the bat); mainly with people producing minimal or timid movement.
Ultimately, these issues tend to disappear once you've spent a bit of time acclimatizing and getting used to it... but this kind of feedback is valuable in helping me know where to focus to make it better *right off the bat*.
2. Yes, that certainly is a bug. I'll have to test it a bit more as you describe it - but I recently solved a problem very similar to what you're describing; hopefully that solution has caught the same issue you're experiencing.
3. There is some ability to grip flatter terrain (it's what allows for you to grab the ground while prone), but relaxing the angle too much essentially makes everything climbable. Which isn't a terrible thing, but it's also kind of a 'game breaking' thing - not that there is a game to break per se; merely that I wanted to show that the system could have reasonable limitations. The angles and the rules of climbing can certainly be altered according to many different elements (e.g. a stamina grip system, equipment, etc). But I don't have specific plans to do it with this demo, because I wanted to focus it more on the walking/movement aspect.
Yes, the plan is to build it as a plugin for first the Unreal system and then the Unity Engine so that I can help get this functionality far and wide in VR. That said, I've had to deal with a lot of non-development work recently, so work has slowed down a bit; but hopefully the time I'm investing into the non-development side now will help speed up future development.