It's a day for 3rd party releases it seems! CrazyEddie has announced that CEGUI
0.4.0 has now been released, the major new feature being the ability to
define custom GUI skins entirely through XML rather than having to
write a custom 'look' DLL. There are also lots of other changes, see
the full news posting for details.
According to CE, OGRE users should be able to upgrade to CEGUI 0.4.0
with few, if any, code changes, since only people who defined custom
'looks' should be impacted by the changes.
Edit: I should have pointed out that you will need to be using
the source release of OGRE to upgrade CEGUI yourself, rather than a
prebuilt SDK.