My only worry about software working with this model (one time fee, download install etc.) is the source code. Things like this, particularly, will need to be easily modified and extended to fit into certain environments, and with no sample source code it's very hard to know how easy that will be. Obviously don't open-source, that kills your business model, but maybe it would be nice to provide a few sample files, or even a stripped-down "basic" version, just so we can get an idea of your coding styles and see if we'd be able to extend the code to fulfill our needs. This isn't a specific criticism of this software, which looks cool and seems to provide a lot of the features of the more expensive enterprise-y solutions at a much more friendly price point, it's just a general criticism of software on this model.