Some of my thoughts:
The dismissal was done by the President in the most harsh wordings possible for a president, loss of confidence, it has happened only once before in Russia thus far.
Most likely the Luzhkov supporters in the city apparatus will resist in the forthcoming period as Luzhkov had an enormous power basis. He'll be charged with criminal charges.
This is a clear sign of the President that he isn't the puppet of Putin as many thought. Luzhkov is a very high ranked United Russia person so my guess is that there is a power struggle in the Kremlin going on. This event will make the President more popular.
I liked this morning the radio reporter of Echo of Moscow "Everything these days is made in China, even the dismissal of the Moscow Mayor" (as President Medvedev is on a state visit in China)