If the IMF no longer uses the "in transition" group, it must mean that they feel it no longer reflects a significant economic difference.  To see if this is true, I have plotted the 2007 PPP-based per capita GDP of various countries.  The data comes from the April 2008 IMF World Economic Update.  The countries classified by the IMF as advanced economies are in dark blue, the countries designated by the CIA World Factbook as "in transition" are in light blue (except for Slovenia, which is now classified as advanced), the countries designated as "least developed" by the UN are in red, and the remaining countries are in orange.  As you can see, the group of advanced economies is distinguished by their high GDP/capita, and the group of least developed countries by their low GDP/capita, but there is nothing to clearly distinguish the "in transition" countries from the others. 

)}}Classifications by the IMF and the UN]]
Since the "in transition" classification is no no longer used by the IMF and appears not to be useful, I suggest that it should be dropped from the map.  Also, it would be better to use current data for the lists of advanced and least developed countries, instead of the obsolete data used by the CIA World Factbook.  I have prepared a possible replacement map on the left.  It shows all countries classified by the IMF as advanced in blue.  The other countries, designated by the IMF to be emerging and developing economies, are in red (for those classified as least developed by the UN) and orange (for those not so classified).