I went ahead and updated to 1.5. I'm absolutely LOVING the new powered and detector rails (boosters without the risk of lag!).
As soon as there's a stable-enough server version and it's loaded up, I'm going to revamp/finish that goddamned Bridgeport-Arena Monorail I started with some shiny new booster rails.
(And if I felt I was really super awesome at Redstone, I'd even find some elaborate system to make sure you can't leave one end of the station if someone is heading from the other end. :P)