David,
I just started a new Smalltalk project last week, my employer is a Smalltalk shop. I am doing a project to load test our servers with several thousand concurrent sessions. I am using VisualWorks and a technology called OpenTalk, for distributed communication. You can distribute your tasks using OpenTalk over several VisualWorks images. It is very fast and much better than Java RMI.
I recommend something like the Manager Workers pattern:
2004_Ortega-Arjona_TheManagerWorkers.pdf Best Regards,
Tim Dion