The last time I was in Moscow, in 2004, there were a number of subway bombings — though outside the stations, not on the trains or platforms — and a couple of airliners were bombed. Then came the Beslan school siege. In aggregate, these attacks were designed to instill fear, but at least to my eyes they did not.
The Putin administration, while vehement in its rhetoric that it would root out evil-doers, basically returned to business-as-usual in its public face. No reason to disrupt confidence in the government. The public, inured after years of such attacks, seemed to brush them off. I would hope they can move forward so easily after this most recent spate of bombings. There's nothing more terrifying than a subway attack, and it seems these were calculated, cruelly, to cause maximum civilian damage. Lubyanka station, across the street from the old KGB (and current FSB) headquarters, was a symbolic target, but also a heavily trafficked one at the city center. Park Kultury is also one of the city's busiest stations: it's on the ring line where several lines converge.
The image above gives a hint at just how crowded the Moscow metro — one of the great glories of modern urban design — can be; it is taken at the Kievskaya station, just one stop from Park Kultury.