The Liv-Ex blog has a great post about the En Primeurs Best Values. Its worth a read.
They took a look at 81 chateaux and compared the En Primeur price to the release price from 2000-2007 and came up with a top 20. Some of the names on the list aren't a surprise (Chateau Margaux, Chateau Latour Chateau Lafite Rothschild), but some of them took me by surprise: Chateau Lynch-Bages, Chateau Cantenac Brown and several of the second wines from the first growths.
I've said it before, but it bears repeating. En Primeurs can be a really good deal if you know what you like and when you are dealing with a great vintage, like 2009.