Hm.... you're certainly more familiar with your project than I am... and that's true, putting an entry in a space doesn't mean it'll get picked up. But it's the same with a JMS message - if you're doing publish/subscribe and there's no one subscribed, you can publish all you want and no one will get it. A JavaSpace client can call notify() to get a callback when something gets put in the space - why wouldn't that work with your app?
I've used JavaSpaces on a small utility that searches for copied/pasted code and was suprised at how easy it was to program JavaSpaces. There's an initial hump to get over what with the rmid and all that stuff, but once I got that stuff worked out and wrote some scripts to automate deployment of new clients and such, all was well.