Steve Bellovin wrote:

The only caveat is that their attack currently works on LANs, not WANs, because they need more precise timing than is generally feasible over the Internet.

On the other hand, many of the SSL servers on the web are located in hosting centers, which are LAN-connected to potential attackers who can get accounts on machines in the same hosting centers. The attackers' and targets' servers tend to have routers in front of them, as well as the switches provided by the hosting center, but it's still much more precise than the open net.