One Remote Desktop Client to rule them all, One Remote Desktop Client to find them,
One Remote Desktop Client to bring them all and in the darkness bind them.
Welcome to Remmina. Remmina certainly isn’t unique in the way that it covers all the remote protocol bases (well except for IPMI 2.0, maybe that’s a feature request developers?). The remote desktop viewer bundled as standard with Ubuntu also covers RDP, VNC and SSH, but it doesn’t offer the same level of usability, or the spit and polish that makes a killer app.
Rather than cover all the ground of Remmina features I am just going to stick to the nice touches, that make Remmina indispensable, in my opinion.
Adding a new connection is simplicity itself. Double click the 
icon, choose the desired protocol, and type in a host name. You don’t need to specify any more than that and it will default to a reasonable set of performance options, for a typical internet connection.
With SSH connections Remmina will use an Identity file as simply as clicking “identity file”.
Similarly you can specify user names and port numbers in an intuitive way, by pre-pending the hostname with the username and an @ sign, and following the hostname by a colon and the port number.
2 really nice features for VNC and RDP connections are scaling and keyboard capture. On my laptop a 1024×768 size RDP/VNC session will not fit entirely on the screen. Scaling comes to the rescue by reducing the size enough to avoid scrolling.
To scale the window to fit your desktop simply click the 
icon.
Instead of capturing a limited set of key combinations, such as crtl-alt-del, you can tell Remmina to capture all keyboard by clicking the 
icon. This is really handy for putting unusual key combos in that would normally be processed by the local system.
Finally Remmina makes creating a reverse VNC connection simplicity itself. When creating the connection choose “VNC Incoming” as the protocol and you are away. To start any connection double-click.
If SSH connections are unbearably slow it is probably because you are running an older version of libssh which contains a bug. Best recommendation in this case is to Upgrade to Natty Narwhal. This will also give a copy and past menu (available as of version 0.90 under the “cogs” icon) which allows copying and pasting from external programs to an SSH window.
In conclusion Remmina is a fabulous open source application, if as much thought and design went into all other open source apps. Redmond and Cupertino would be quaking in their boots!
References:-
http://remmina.sourceforge.net/
https://bugs.launchpad.net/ubuntu/+source/libssh/+bug/663777?comments=all