  The Chandra Carina Complex Project (CCCP) has shown that the Carina Nebula
displays bright, spatially-complex soft diffuse X-ray emission. Here we `sum
up' the CCCP diffuse emission work by comparing the global morphology and
spectrum of Carina's diffuse X-ray emission to other famous sites of massive
star formation with pronounced diffuse X-ray emission: M17, NGC 3576, NGC 3603,
and 30 Doradus. All spectral models require at least two diffuse thermal plasma
components to achieve adequate spectral fits, a softer component with kT =
0.2--0.6 keV and a harder component with kT = 0.5--0.9 keV. In several cases
these hot plasmas appear to be in a state of non-equilibrium ionization that
may indicate recent and current strong shocks. A cavity north of the embedded
giant HII region NGC 3576 is the only region studied here that exhibits hard
diffuse X-ray emission; this emission appears to be nonthermal and is likely
due to a recent cavity supernova, as evidenced by a previously-known pulsar and
newly-discovered pulsar wind nebula also seen in this cavity. All of these
targets exhibit X-ray emission lines that are not well-modeled by
variable-abundance thermal plasmas and that might be attributed to charge
exchange at the shock between the hot, tenuous, X-ray-emitting plasma and cold,
dense molecular material; this is likely evidence for dust destruction at the
many hot/cold interfaces that characterize massive star-forming regions.
