Mike Gaultieri, a analyst at Forrester Research, takes application developers to task for not knowing what the business wants.
This has never been more the case than in the case of event processing. Without understanding the business events that are available to them and the needs of end-users, developers are not going to get anywhere. What do I mean by business event? It's simply an event containing some business orientated, rather than technically orientated, information - a stock tick, weather report, GPS coordinate etc. It can be pretty much anything, but it must have some business value and meaning to the business.
In addition, developers need to understand what the business wants to achieve - is it about simply maintaining an up-to-the-moment view on a goods ordering process, using appropriate charts and graphs to visualize the information, or is it about automating decisions - pricing a product dynamically or re-routing a vehicle based upon traffic conditions? Often, an end-user won't care about what technology is being used to deliver the information or make the decisions they want - and nor should they. As Mike Gaultieri correctly points out, a good user experience is everything; the technology itself is at best secondary or often irrelevant.
My advice to developers is to start small and focused, get something done and prepared to iterate quickly. Try and define business requirements to begin with but be flexible about changing them (within reason). If developers don't do this, and work in a vacuum, success won't come.