At the recent 2008 Serious Games Summit at the Game Developer Conference (GDC), Shawn Firminger , studio manager of Aces studios, delivered a talk outlining the development journey of Microsoft ESP.
An account of Shawn's talk has been posted at Gamasutra and is well worth reading.
In the talk Firminger emphasizes ESP's Microsoft Flight Simulator heritage. Flight Simulator is Microsoft's longest in development product, being in continuous development for 25 years. Firminger describes these years as ESPs beta period.
The first attempt at creating a training platform derived from Flight Simulator, was in 2004. At that time, Firminger mentions that Aces failed to convince Microsoft sales executives to support the development of such a product. (Note: CFS4 was cancelled in 2004/05 also.... though I have a feeling that CFS will be reborn at some future date.) However the success of Flight Simulator X together with its developer accessible API and SDK and also with train simulator sharing the same core technology, Aces second attempt to create a training platform met with success in 2007.
Shawn also emphasized that it is important to have the support of your sales department if a project such as this is to have success. He also emphasized that ESP is a serious games platform rather than a serious game, which are a different 'beasts'.
The GDS ESP presentation is also featured in a post at ausgamers.com
The Ausgamers' article further mentions Microsoft's long term commitment to ESP with a roadmap planned many years into the future. Plans for version 2 and 3 of ESP are still in process, however that article mentions that the next version will see more focus on ground elements with marine elements further down the track.
For further information check out the Microsoft ESP home page.