A lot of wank in this thread, a lot of misinformation. Azeroth is not the size of Earth at all and most of the travel time feats posted here omit facts about what sort of journeys are being undertaken and how. The most accurate and straightforward journey made that can be used to properly measure the size of Azeroth comes from War3 where the Nelfs journey by boat from the top of Kalimdor straight to the bottom without making any stops in 3 days.
Actually, the Eastern Kingdoms on the Argus Azeroth is the vanilla version, Gilneas isn't there. Kalimdor however, is the post-Cataclysm version, with Azshara being blown into a Horde crest.
Additionally, the EK is missing Ghostlands/Eversong Woods/Quel'Danas while Kalimdor has Azuremyst Isle under some clouds, it's interesting what you can find out by looking at the texture files. :p