You will have to check it out (since you phrased that as a question).
You can play multiplayer over the internet (in addition to the already plenty fun single player mode) collaboratively or competitively (or a combination, i.e. teams). I'm always trying to get new people to play, because I think it is a great game that deserves a large following (not to mention user contributed extensions, which you all should definitely get into making!), but it's not very popular in America.
Actually, it is a little weird, but the game seems really popular in Europe. Most of the players on the online servers are Danish, Dutch, German, etc. I guess they just must like trains (and planes and ships and trucks and trams) more over there.
Maybe I should start a topic in the "reviews" section and see how many people I can get interested in this game...
Anyway, until then, if you want to try playing on your own but don't know where to begin, I highly recommend checking out the wiki at
http://wiki.openttd.org/. Some of it might be a little out of date, because a MAJOR new version was released this week that added some great new features to the game, but some of them might not have been documented there yet. Still, its a good resource if you want to learn about traditional "Block" signaling (and the complicated junctions needed when using that type of logic) and has some information about the benefits of Path Based Signaling (PBS), although it does lack pictorial descriptions of more complicated track layouts using PBS (check in the discussion pages, though, because sometimes someone will post a really helpful explanation or image there).