A moders dream!!!
The best thing (well at least for me) is that the game is really easy to mod. Want an additional bus type? 5 min (including the textures). Want new texture? 2 min? Want to change capacity of a subway train? 1 min. Anything you want just open Notepad and edit. This is why I have two installs of the game - one clean and one moded so much that I don't even know what I've done :D.
The game actually grows on you with one more thing - map editor. Create your home city or make a fictional city of your own. So far I've spent more time in this than the game itself.
In some words - gameplay is not so great as you want, but you can easily change it.