We often have to lock down the user interface when we are installing systems that are used by the general public but any personal user will want to be able to access Windows XP to install their own 3rd party apps.
Lots of people see the huge potential here. With the price of hardware always falling these systems are only going to become more attractive. We are flooded with request to add custom features and services like GPS Tracking. Having one system that can play movies DVD,Music,GPS,Tracking and go online offers huge cost savings for most companies. There is no need to replace lost remote controls, one system replaces 3-4 different peices of hardware and is supported by one manufacture.
Open Source VS Commercial is tough. I am a big supporter of open source but at the same time have to make a living selling and installing systems. It would be nice if we call all agree on way to talk to our front ends. That way people on these forums could develop plugins like the calander you were talking about and they would be usable on any interface.