Are you using this for digital stitching or heavy swings/tilts? That's the only reason to buy the Digaron-W range.
if you are using it single shot work on Digital MF, then you are better served by the Digaron-S range (formerly 'Apo-Sironar Digital HR')
These have much higher resolution, faster apertures, and near zero CA.
Expensive, but its an incredible 15 element design... compare the MTF charts at Rodenstock's site.
but - if you are stitching, then indeed the -W is the one.