The more I think of it, the more I believe SaaS is not the right model for heavy-process transaction-based applications. Certainly appropriate to manage data-intensive applications (e.g., customer interaction data à-la Salesforce.com) but not so fit when integration and STP are the business imperatives. I don't have a final position on this matter, but I will investigate more on it, as the impact on treasury management systems (TMS) can be quite devastating. I'll keep you posted on my research, and please feel free to inject comments.