I tried it with the default exposure of 1.6 and it was ever-so-slightly different from rendering without it.  There was better handling of areas of the image that were only lit by indirect (bounced) light, but it was hard to tell.  I am re-running with exposure at 2.2.
oops, ps: mode is Exponential
edit/oops again: since Bagginsbill suggests that Exponential is pretty much useless, aborted and restarted as HSV Exponential

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