In a lot of workplaces whenever one person is out, another person has to make up for it by doing the person who's outs work in addition to their own work. Not saying it will definitely be the case here, but it could be.
The long term success of that strategy indicates the extreme likelihood that the 6 hour people will get the same work done as the 8 hour people, just the 8 hour people will browse facebook and gossip for 2 more hours per day.
The interesting part of the analysis is that obviously a 8 hour workplace can handle a fraction of the employees calling in sick pretty much transparently. Now what happens when everyone works 6 and there theres no slack WRT sick days?
From personal experience the time and monetary savings of four tens is far more appealing to me than the idea of spending perhaps nearly a quarter of my time away from home, going to / from work. As a starving student I worked 4 hour part time shifts working while going to school... at $1/gallon gas it barely made sense, now gas being permanently around $4/gallon I don't think short shifts make sense unless your commute is extremely short or you make a substantial amount of money per hour.
If I work 4*10, I barely get to see my son anymore. I wouldn't mind slightly shorter days; we already sometimes struggle with who has to pick him up. Technically my wife should do it, because she goes to work much earlier than I do (I bring, she picks up), but sometimes she has late meetings on the other side of the country, whereas I work on cycle distance from home.
