[Johan Hiemstra]

It's working fine for me, I can't confirm 4.0.7 specifically but the beta seems to refer more to it being unfinished rather than unstable.

I suggest creating a child style of your own and make the template modifications there (if you're going to make those manually), but if if you revert those you can easily change back. It's more a cosmetic thing.

The main thing it does is give you an additional option in the admin panel, which you can use to generate the sprite image.

There seems to be a problem with adding more than one custom icon but with just the standard icons it includes by default it's still a very useful mod.

That said, you should always create a backup before making changes like this.