Well... I haven't used the Metro (the subway system in Copenhagen) daily for a couple of years now, but still... aside from the fact of increased awareness of possible terrorist attacks, I think the Metro has risen to the expectations of a lot of residents.
It had a few, to say the least, "childrens diseases" early on, which became very taxing. But I think they've gotten a good grip on it now.
There are political discussions on expanding it farther than what it is right now. The first part, which has been decided on but has yet to be finished, is connecting it to the Copenhagen International Airport in Kastrup. According to their homepage -
www.m.dk (both in Danish and English) this part of the construction should be finished during the last quarter of 2007, connecting Vanløse in the outskirts of Copenhagen over Kgs. Nytorv (the square which among other things features Nyhavn, a famous part of the Copenhagen Harbor with taverns and restaurants spread on the lenghts of the dock-side, and the Gammel Scene, which until the opening of Operaen - the newly build operahouse - was the main stage of the Royal Danish Theater) with the Airport. Making the time a trip from the centre of Copenhagens old city to the Airport takes a fraction of what it is today.
The next big project of constructions on the Metro is the Cityring - a part of the Metro not yet agreed upon by the politicians, but which is supposed to go through the political system without much trouble. But we won't probably see this part of the project realised for another 10-15 years or so.