I think, (Much like redstone) Mabybe you should make it a little more clear which side is the input (I notice the the input usually has a longer peg) But it was kinda hard for me to figure out when I was first playing the game, other than that it is pretty straight forward! P.S are you going to add things like pistons, spinblocks, wheels etc.?
Personally I like that there is no explicit tutorial that tells you exactly how each component works; you have to do some experiments and figure it out on your own. With TUNG I want to recreate the feeling I got when I was first learning redstone, where you're figuring things out for yourself and learning as you go.
As for circuit outputs that interact with the world, I don't know. These things work well in minecraft and other sandbox games because there's an existing world to interact with, but TUNG's world does not exist in its own right. Its sole purpose is to be a location for the circuits you're building. For the duration of alpha, at least, the focus will be purely on the digital circuitry aspect, but after that anything could happen. You could probably make mods for all those things right now though: the fantastically talented pipe01 has built a modding framework for TUNG.
I agree with you on the fact that it's fun and rewarding figuring out for yourself, I just feel like later down the line critics won't share the same enthusiasm.