I really like the computer screens that are being displayed in many of the screenshots, but I think they have potential outside of decoration. In the water demonstration video, the developers unleashed the water by manually breaking blocks to let the water through. I think it would be interesting to have the active/inactive blocks from Terraria and have them hooked up to those screens to activate. For example, when just used as decoration, the screens could be their normal blue color. When a device is hooked up to it, the player can choose the screen's color between red and green. Whenever the screen is interacted with, it activates the blocks it is attached to and flips to the other color (red/green). So, using the water demonstration video as an example, when the block is keeping the water held back, the screen could be green, and when you want to retract it, the screen turns red. The colors could also be reversed based on your preference! Sorry I'm not great at explaining. If you don't get what I'm trying to say, let me know, but if you do, I'd love to hear your thoughts.
Basically, all circuit objects have an active/inactive state. You can program which of these two states causes a red or green screen, and then you can activate them from the terminal you wired it up to. So, if I wanted to make a bridge out of inactive/active blocks, I would probably set the terminal to show red when they're inactive, and green when they're active. On the other hand, if I was using one of these blocks to lock a door by blocking it off, I might have it green when they're inactive, and red when they're active. Just a personal choice.
That actually would have been a much better way of wording it, but basically yes, it's a switch. Just a much fancier, more colorful one. If I wanted to wire up some lights for one room, I might use a regular lightswitch. If I wanted to set up a lighting system for my whole house, I might use one of these instead.
I would rather see these computer screens act like the (unreleased) 0x10c computers, or computercraft(minecraft mod) type computers.