Released Amethyst version 0.8 yesterday. It has some significant improvements to stability as well as adding a few new features. There's a new column layout that tiles windows into full height columns and the addition of floating windows. It can be downloaded here or installed via homebrew cask.

Floating Windows

I had a request for floating windows and it's now in the app. mod1 + t can be used to toggle whether a window is tiled or floating. A floating window will not be tiled, but will be part of the focus chain.

Additionally, you can supply a list of bundle identifiers for which windows will be floating by default. They can be specified by defining an array of bundle identifier strings under the floating key in your .amethyst file. Any application matching a bundle identifier in the list will have its windows float by default, though use of mod1 + t will tile it if you want. I find this quite useful for windows that Amethyst generally can't resize or position correctly (e.g., Photoshop).