Usually Mesa point releases are rather boring with just a handful of bug-fixes each time. For Mesa 9.2.4, there's more changes than usual since a lot of Freedreno driver changes were allowed to be back-ported. This open-source Qualcomm Adreno driver got a lot of improvements in the stable Mesa 9.2 series since its state in 9.2.3 was known to be broken and overall the code is still being raised, albeit it's already the leading open-source ARM graphics driver.
More details on the changes found in Mesa 9.2.4 can be found via the Mesa-announce list. For those waiting for the Mesa 10.0 release, you can read about the many exciting features in the meantime.