Im a HUGE fan of OpenTTD, tell me how is this game compare to OpenTTD
It is like TTD in that it focuses more on the routes and vehicles more than other aspects. There is still challenge though, because you can't just mass-build one type of transit and expect to make money. Traffic is a real concern (build your tramline on the downtown roads and watch as your tram moves slowly blocked by cars, and your buses have trouble moving at all), so you need intelligent route design, such as feeding your buses into your metro stations.
Tramlines are also awesome, btw, because while placing them is tile/grid based, and they can run on roads or cross them, they can also run down the median between double roads (not harming traffic) or through parts of buildings (like the front area of a hospital or courtyard of a church).
The money aspect is a lot like TTD - maybe hard at first, then you figure it out, then it becomes less of "how much can I get" and more to "how masterful can I design this place".
Although your only "cargo" is people, its how you manage your routes and get people around the city with your coverage that matters. The AI people in this game are smart enough to transfer, so you can bus them from their rural homes to the water ferry, which they ride across and hope on a tram, taking them into the city metro. You make more money this way (they pay at each transfer) and its the whole ideal of this game - making a mass transit system that flows together.
There's also a community I found (citiesinmotion exchange) that has user maps, some tweaks (prices/speed/capacity/etc) and some new vehicles and whatnot.
Also, the DLC is very optional (you're only buying a few items with the DLC, the exception is Tokyo since its a whole map + scenarios). So think of the DLC more like "toss the Developers a couple bucks cause you love them, and they want you to have 5 new vehicles". But if you didn't get any DLC you'd never even know it was missing.
All in all, I'm loving it (it isn't replacing my OpenTTD, but filling a side-role).