We've added Retina support for Fluid connections. There are some limitations at the moment thought: It's supported when connecting from a Mac with a retina screen, ideally to another Mac with a retina screen. To get started with Retina mode:

1. Make sure you're connecting from a Mac with a Retina display and make sure the remote Mac also has support for retina.
2. After you connect click Remote -> Displays -> Use Retina Resolution.

Please note: Retina mode requires up to 4x the number of pixels and will have a performance impact on connections. You can toggle this mode and or off any time.