I tried to install vanilla wine from homebrew first, but that is rather difficult right now because it doesn't compile well under llvm, and one of its dependencies needs some difficult to discover flags to build correctly.
Wineskin just works. Grab it from http://wineskin.urgesoftware.com/tiki-index.php?page=Downloads
Once you've got Wineskin Winery.app, run it and install the latest wrapper and engine (I got things working with WS91.5.13). Create a new blank wrapper.
Fire up your new wrapper (located in your home directory under Applications/Wineskin). This should launch the wineskin app. After you've installed some things, it will prompt you to select an exe to run when launched, and it will be harder to get to the Wineskin control panel for the wrapper. You can always get to it by right clicking the wrapper .app, clicking "view package contents" and then launching the contained Wineskin.app.
At some point wine will offer to install mono and gecko. Not sure if both are needed, but I installed both and it worked.
Go to advanced -> tools -> winetricks and install the one for steam. I tried just installing steam from the windows .msi without using winetricks and the steam client was pretty messed up - no text because of missing fonts, etc. That route seemed to work fine using the WS91.4.1 engine, but I wanted to use the latest.
Download Sins via Steam
Everything here should work normally, until the app is downloaded and ready to launch. Gets through the DirectX setup and the Visual c++ redistributable runs but freezes. Just quit out of everything and start it up again and it should skip that bit the next time. Now you'll get to the stardock activation screen. This is where stuff breaks down - the register button doesn't do anything.
Getting Activation to WorkUpdate: supposedly activation tool included with the most recent Steam version works, per https://bugs.winehq.org/show_bug.cgi?id=29136.
For whatever reason the version of the activation tool provided with Sins doesn't work. However, we can get another. We'll take the one from Stardock's Stardock Central app.
Installing Stardock Central
Download the installer here:
That installer didn't seem to run properly through wineskin's install software tool. So we need to copy the installer into our wrapper and then run it from the command line. Open up the wrapper with "view package contents" and drop the installer into the drive_c folder there. Now, fire up the Wineskin app for your wrapper and go to Advanced -> Tools -> Command Line. Change to the top level of C with:
And then run the Stardock Central installer with
Copying the Activation executable
Now once again view package contents on your app. Navigate to
drive_c/users/<your user name>/Local Settings/Application Data/Stardock/Stardock Central
Make sure you don't have any of the Wineskin apps open, and then copy sdActivate and Activate.lng, and paste those into
drive_c/Program Files/Steam/steamapps/common/Sins of a Solar Empire Trinity/
Now fire up your wrapper again, launch Sins from steam again, and this time you should get a different activation window that actually works!
Windowing and Video Configuration
You probably want to run in full screen mode, so configure that from the Wineskin.app for your wrapper -> Set Screen Options. Choose the override radio button, and then the fullscreen button.
I'm running an early unibody MacBook Pro and found that I had to turn down the graphics settings in Sins to make it run smoothly.