What was the commercial speed of Concorde?
The Concorde cruised at 1350mph (~Mach 2.05 at 55,000Ft.) 

Concorde’s fastest transatlantic crossing was on 7 February 1996 when it completed the New York to London flight in 2 hours 52 minutes and 59 seconds.

When it flew the average flight time (was) around 3 hours 30 minutes, but can be slightly longer if the aircraft (needed) to hold before landing at the local airports.

Wind is a huge factor in flying. A headwind or tail wind can mean a big difference in flight time. The Concorde cruised at a significantly higher altitude than most airplanes ~55,000Ft. which means it was subject to very different wind than its sub sonic lower flying counterparts. At that altitude winds in excess of 100Kt are common place. So you could see a 200Kt difference in speed depending on direction. 

Also of note the speed was often called out using Mach's Number (the Concorde flew a bit over Mach 2). However since Mach's number accounts for air density,  Mach 1 at 55,000Ft. is 660MPH which is significantly lower than the often quoted Mach 1 = 760MPH (which is the speed of sound at sea level).  

One of the best sources of info on flying the Concorde is this podcast interviewing one of the pilots.