Nice to hear from you.
I'm using the 2013.1.8 release for 4.0. My app is compiled for .NET 4.5.
In general I've found the library to be pretty reliable, and like you, I'm very grateful that it was written and is being maintained.
Our application regularly launches 20 - 40 virtual cloud computers and then interacts asynchronously with them via the Renci SSH library. I use C#5.0's new async features and Task.Run() to start SSH activity concurrently on multiple threadpool threads.
Each thread follows this model: open ssh connection, do activity (file upload or download, or exec remote command) and close connection. None of the files are large and none of the remote commands take more than a second or two to finish. As I mentioned above, there may be between 20 and 40 such threads running at the same time.
A given run of the application can last for 72+ hours and thus issue 20,000+ SSH requests before it ends (the program interacts with the virtual instances about every 5-15 seconds, to put a file , get a file, and so on)
Sometimes the app can run a whole weekend and everything is great. But too often, one of my calls to Connect() never returns. I'm checking for exceptions but in these cases am not getting one. I emit a debugging message before the connect and after the connect - I get the debugging message before the connect, but not the message after the connect.
I hate to switch to another library because I have 8+ months invested in using and testing with this library, but this particular problem may force me to switch libraries.