https://github.com/openscopeproject/TrguiNG
Builds for all platforms are available in release page.
I consider it to be in beta: stable, functional and usable but may need some polish here and there. Please report any issues you may find if you try this app.
Here are some features that make it stand out from most clients:
* Multi tabbed interface for concurrent server connections (native app only)
* Torrent creation with fast multi threaded hashing (native app only)
* Powerful torrent filtering options
* Latest transmission features support: labels, bandwidth groups, sequential download
* Dark and white theme
* Works as windows/linux/mac app or as a web interface served by transmission itself