Mansion poker is a top-notch site, but don’t expect them to release a Mac version of their software any time within the next year or so.
Here’s the response Mansion member services sent me:
We are not currently working on Mac compatible software, however it may be something we will introduce in the future.
They’re really missing out on a lot of players, by not having an option for Mac users, and they probably don’t realize it. Maybe when pokerstars releases their Mac version, sites like mansion will give the idea of Mac poker software a second thought.