WebSphere Portal Server 7.0 has introduced a concept of portal light mode, which is supposed to improve start up time and memory consumption of production environment. But interestingly it still has support for enable-develop-mode-startup-performance
The WPS 7.0 Info center has following information about enable-develop-mode-startup-performance task "The developer mode allows you to improve start up performance and to configure IBM WebSphere Portal for development. Developer mode is for a development environment only and should not be used in a production environment. Install WebSphere Portal with the Base installation option."
From the documentation it looks like the portal light mode is only for the production environment. When i tried running this task on my local WPS 7.0 installation, i did not get much improvement in the server startup performance the startup time for base installation is close to 9-10 min. Also i did not see any change in the memory size of the server.
But when i executed the enable-develop-mode-startup performance on my local i could see that the server startup time came down to 5 min from 10 min and also the memory size came down from 700 + mb to 500 mb.