Check out the features.
Download and install. Note that this is still a developer build.
Things that struck me and made me yell "whoohoo!" (and there are more) are:
* Ability to insert new columns when there are merged cells in that area
* Pressing Shift - F4 lets you toggle between absolute and relative cell references and it applies to a group of cells, whatever you select
* Way more than three criteria for the standard filter now
* "Create new style" button in the Conditional Formatting window -- not as good as just defining the formatting without styles but very close to the same thing