I second this question, not because of the shared instances (which sounds also interesting for me), but because of the limited available memory within my VPS. I've seen -Xms64m -Xmx64m (and vice versa) options in another thread. Would they really help to decrease the memory consumption?
Of course I'm not expecting a fast server, but it would be nice if it can leave some space for other processes :) Because SCM-Server is the most memory hungry process I have right now (with default settings).
Cheers,
// Murat