How is the Warsaw Metro
Clean (even a bit sterile), efficient.
and how is progress going on it's extension?
It isn't. The first line probably won't be extended. Ever. There may be one or two new stations, like the pl. Konstitucji station (actually by ul. Wilcza in the premises now used by a gogo bar, called Chilli) and pl. Inwalidow, which were planned but not built. The second line is in the technical planning and finance stage. The original plan was to have part of the second line running for Euro 2012. This won't be, but they should have started before the end of next year. Most of it will be 'cut and cover' rather than tunneled which should make it quicker. The third line's route isn't agreed yet. I'll see if I can find a map of the second and third lines and add as an edit.
how is public transit generally in Warsaw, whether light rail (trolley), bus or regional rail.
Buses and trams are generally good, and EU membership has allowed modernisation. Trolleybuses (Warsaw to Piaseczno) were stopped amid protests a few years ago. The WKD (light rail to the Western suburbs commuter towns) is being upgraded. Local trains are significantly improving, but slowly, and with beaurocratic arguments. Small suburban stations are being upgraded with EU infrastructure grants - but the service is still so bad that they are under-used.
There was meant to be a tram to Wilanow two years ago and was never built. This is now a problem due to thousands of flats and no transport infrastructure. A bigger priority is Tarchomin, north of the city. There's meant to be a new bridge with some sort of rapid transit connecting them to the metro. Land has been bought, tenders submitted for building, but no significant progress yet. The people who live there wish there was.
Still no airport trains. There's a station a few hundred yards from the terminal, but no easy way to get there and not many trains stopping there. The plans to re-route the WKD past the airport came to nothing.
One problem is lack of co-ordination between services leading to public arguments between the different providers. This has improved lately, with the monthly ticket now working on train and WKD.
A bigger problem is that the small towns around Warsaw have a high degree of administrative autonomy, and there is no one central body to co-ordinate transport in the Warsaw 'travel-to-work' area. This has led to the Warsaw bus company threatening to pull transport to Piaseczno and putting posters on the buses about that (threat now averted), and a bewildering array of mini buses and private companies with no central timetable or co-ordination.
This is a bit old - all of line one is finished. Line two will cross at Metro Swietokrzyszka (that's why it's such a small station - only half has been built). They can't cross at Metro Centrum due to a certain very well-known building, too heavy to tunnel near.
Line 3 is a very, very long way off, but will probably cross line 1 at pl. Konstitucji and have a station at pl.Trzy Krzyzy.
You might like this site about the metro: