You know you can make the side windows disappear by clicking the yellow "x" button ;) and I think it can be disabled by default.
As for the skin.. there's many skins for 2.3 that is free
http://resources.invisionpower.com/index.p...&showcat=84
http://skins.invisionize.com/db/index.php/c/241
IPB 3 is an incredible software especially adding mods is so easy and just works great. People who add mods really appreciate the new format.