If the player is in the tractor beam, it will drag them up towards the top. It drops down really far (about 100 blocks, but I'm thinking of raising it to 500). The purpose is to give the player the ability to dig very deep down into the belt. It's a lot more dense down there, so they can get more minerals than if they were to stay on top.
Eventual plan is to also let it be used to communicate. By building a dispenser at the bottom of it and connecting it to a chest, the player will be able to transport blocks back up to their base without having to go back up.
I think I'm going to force the player to keep water near it. Since it uses a lot of energy to create the beam, the equipment heats up. The water can help it stop from overheating.
Not sure if I'm going to force them to attach a pipe or just submerge the elevator. Oh, one thing I forgot - the elevator can be between 1 and 5 blocks wide. The tractor beam will always take the center block though.
Here's a 1080p video I just created showing everything off: http://www.youtube.com/watch?v=KNF9_FVXlgc
So that's it for now. More updates later this week :]