The remote API is powerful, however the plain text data returned by the server is awkward to work with. It would be better if there was an XML based API using a SOAP or REST interface. This would make developing applications that interface with Virtualmin much easier.
Previous to the announcements about AgileBill's integration with Virtualmin i spent alot of time writing my own accounting and hosting control panel, its simple but fits my needs exactly. I'd love to integrate it with Virtualmin, but as it stands it's quite a messy job.
So how about a SOAP wrapper for the exising service?