Gentlemens and Mentlegents, boosters have now once again been unintendedly been introduced in minecraft; not to the same extent as last time, but still.
the new boosters cannot amass momentum by side by side carts but instead relies on the slightly more older spin-booster.
the cart can now only gain momentum while occupied, requireing more clever railworks.
here is a video about it (not mine) http://www.youtube.com/watch?v=bBiHnP0R6M0