Yes, the transporters in TADPSID are functional. The closest transporter is on Birmingham Island, you can see the exact location in this screenshot:


To use a transporter in TADPSID:
1) walk into the transporter, and look around to see that you're completely surrounded by metal (yes, I deliberately went for an impossible design)
2) push the number of the transporter you want to reach. I mean in the main keyboard, NOT in the numeric keypad. You will hopefully hear the familiar transporter sound
3) exit the transporter

Transporters can also be used in this way in Damocles and Mercenary 3, if you stay inside the transporter and press the number when all you see is white.
In both of those games, and in TADPSID as well, the transporters can be picked up and carried around, if you have the antigrav in your inventory. If you reach a transporter when you already have another one in your inventory, you can still select the one in your inventory. Let's say you picked up transporter 2 and you are near transporter 3. Enter transporter 3 and press 2 on your keyboard. When you exit the transporter, if you're playing the original games, you will be in a building that contains the objects from your inventory, and the only way out of that building will be the transporter that you picked up.
In TADPSID it's almost the same thing, only there's no building involved and the transporter will be floating in a white "inverted space".

About the speed problem you reported: have you tried activating vsync from your video card options?
If it does not work: I am aware that the current routine that calculates the amount of movement for every frame is approximative. I already replaced it with one that is more precise, that will be present in TADPSID v9.
Also, be aware that you don't need to travel at a particular speed to leave the planet, you just need to reach a particular altitude.

In the current (already released) version of TADPSID, these are the things you can interact with:
- vehicles in various locations
- beacon locators on Logos, near transporter 7 (if you pick them up, you can see red beacons and blue beacons)
- a hand weapon, near transporter 8 (if you pick it up, you can shoot while on foot)
- the museum guide on Cronus (it works almost exactly like the one in Damocles, except that you can also scroll the list with the + and - keys on the main area of the keyboard, as well as use TAB as an alternative to * to display the current entry). On Cronus, you will notice that I expanded the museum to add objects referring to events of Damocles and Mercenary 3.