I was hoping to take a fairly serious standalone Swing desktop application (no server involved) and use Terracotta to replicate a simple user interaction between two instances.

For example, I'd start up two instances of the application and update something in the model via one instance and watch it get updated in the other instance.

The application I had in mind is substantial although I was only interested in distributing one model from it (albeit a very large and pervasive one).

This was an artifical requirement and had no practical use for the application in question. The hope was to find out how easy it was to use Terracotta with something that wasn't designed with this behaviour in mind and whether a noticeable performance overhead was incurred. As it turns out I never got it to work - the model was far too complex to be a successful candidate for clustering; Terracotta demanded that I distribute more and more components until I finally came to the conclusion that while clustering may be relatively trivial to implement with Terracotta it's still not something you can retrofit into an unaccommodating design. Kinda obvious in hindsight.

I hope to give it another go someday when I get the time, but perhaps on something a little more amenable!

If you want to get a feel for the overhead and performance, though, you could do a lot worse than trying out the examples that come with Terracotta - they're basic but pretty good.