Arrgh, just as I break one cycle of addiction, another threatens to start:-)
My baby sister has Rollercoaster Tycoon on her PC (which was my old box which I gave to her). We'd spend four or five hours at a time when I was at home designing theme parks together. It was good sibling bonding. Casino Tycoon is also a lot of fun, but Transport was the original and the best. This promises to be very good.
 Picking unhappy guests up and dropping them in lakes.  Making the magnetic-induction vertical coaster just *one* section too short at the top; the pause as the thing comes off the rails is just *poetic*.  Creating flux curves without roofs on water slides and watching punters on dinghies fly off into space.  Seeing just *how much* yak a Stand-Up Vertical Coaster can induce.
I'm really proud of my signature coaster part - the Bow Tie. It requires two half loops and a corkscrew then loops round itself twice - just like a bow tie. I'm also v fond of putting two vertical loops at 90 degrees to each other so that one goes through the middle of the other.