Long-standing fan, with boxed copies of Transport Tycoon and Transport Tycoon with World Editor, and a budget copy of Transport Tycoon Deluxe (DOS version). Somewhat irked that Locomotion dumbed-down so much, and completely gave up on the original TT manual preface's promise to not make the AI gratuitously cheat. Thanks to all the OpenTTD devs for backporting most of the cool features and raised technical limitations from it to TTD, and making it cross-platform too. :)
I tend to build large, heavily interconnected networks with incredibly complicated high-traffic junctions, treating TTD as more of a puzzle game than a realistic simulator. I like neat and well-defined routing features, such as one-way track (original TT didn't even have that), presignals and waypoints.
I've turned a couple of stubs on version 0.6 features into full articles:
I also posted a little about the martian climate from World Editor, or "alternate graphics", as it was known in the UI. My contributions page should list any other little miscellaneous fixes.