The NYT had a useful piece on the increase in the number of people working at part-time jobs who would like full-time employment. This is an important measure of under-employment in the downturn that is missed when people just look at the unemployment rate. Since part-time workers often lack benefits like health care insurance, this can be an especially important issue.
However the piece concludes by equating part-time work with flexibility for employers. This is not true. There is no direct relationship between part-time work and flexible hours. A worker who has a regular shift from 1:00-5:00, Monday to Friday, provides no more flexibility to an employer than a worker who works from 9:00-5:00 the same days.
The flexibility comes from the fact that part-time workers are likely to have less bargaining power than full-time workers and therefore may have to accept changes in work hours on short notice. But this is a different issue than being employed part-time.