Since creepers no longer do block-damage (entity only) on the server, it is safe to build above-ground rail systems.
If you want help with using redstone to switch tracks, or using powered boosters, just yell. DE, Pra3, Infernal, and myself are all willing and able to help (not sure if others are well versed, if so pipe up).
For long-distance boosts, we use the old booster cart method with one-way or two-way self resets. If you need help with these, Pra3 and I have made a ton.
Using carts in the nether is an extremely fast and economical way to travel. It would cost ~480 iron to build enough tracks to go 1.28KM in the real world, whereas you could traverse the same distance between two portals in the nether with ~30 iron.
To put it into perspective, the ~8KM HTP Express required ~3000 iron, approximately 2 seasons of battlestar galatica, 4 seasons of STNG, 1 season of Bones, 2 seasons of Dexter, several viewings of both seasons of Frisky Dingo, and several feature length motion pictures worth of digging.
Utilizing the nether instead would have taken about 4 hours, and approximately 83 iron, 20 obsidian, and some cobble or stone to make the trackbed.
I don't want to talk about it anymore.