Flying cargo and IFR on singles will give you a great experience but not necessary the proper one for an Airline.
From my point of view, this is exactly the type of experience that is useful. I feel the schools that put out the ab initio's do a good job of training, pilot's can probably out type me on the FM, some of the weak areas I see are items like, cockpit discipline, like the one where someone should be looking outside :
, I wish I had a dollar for every time I see one of these wiz bang (I know the SOP's) FO's, types in the new wind direction and velocity when they are the flying pilot on a three mile final.
