Xee³ was created as an almost complete rewrite from scratch of the older Xee 2.2. If you for some reason prefer Xee 2.2, or if you use an older computer which can not handle Xee³, the old version is still available for free on the Google Code download page:
Note that this should not be used as a demo version of Xee³. Xee³ contains many large changes from Xee 2.2, and they can not be directly compared.
Also note that development has ended on the 2.x branch of Xee, so no new features will be added, nor will bugs be fixed. However, the source code is available, if you want to make changes yourself.
Xee 2.2 should run on both Intel and PowerPC machines, on Mac OS X versions as far back as 10.4.