  Supergiant Fast X-ray Transients (SFXTs) are HMXBs with OB supergiant
companions. I review the results of the Swift SFXT Project, which since 2007
has been exploiting Swift's capabilities in a systematic study of SFXTs and
supergiant X-ray binaries (SGXBs) by combining follow-ups of outbursts, when
detailed broad-band spectroscopy is possible, with long-term monitoring
campaigns, when the out-of-outburst fainter states can be observed. This
strategy has led us to measure their duty cycles as a function of luminosity,
to extract their differential luminosity distributions in the soft X-ray
domain, and to compare, with unprecedented detail, the X-ray variability in
these different classes of sources. I also discuss the "seventh year crisis",
the challenges that the recent Swift observations are making to the prevailing
models attempting to explain the SFXT behaviour.
