It's not the revisions, it's the different formats and covers. The Tor Trade PB of March 15 2011 is shown on Amazon with this cover:
It is the large format (21x14cm), but the wrong cover.
The matching cover I'm after:
is only shown as published in Aug 2006 (which must be FPW's first revision and is listed as the Mass Market PB edition) and is only 16.5 x 10.4cm.
I don't want to order the new reprint to get the wrong cover.