
Regarding the D-LUX 4, Leica says "Leica Camera AG has developed its own unique colour matching, contrast and picture definition profile which produces digital characteristics complimentary to Leica M film photography." What we don't know for sure is whether Leica's special profile can be duplicated by making very simple adjustments (eg, noise reduction set to -1) on the LX3.
If you've always wanted a Leica for the name and look of it, there's nothing wrong with buying the D-LUX just for that =). You do get Capture One, a longer warranty, and higher resale value as well.