Wow, this is one of the most intelligent threads I have seen in quite some time (TheHorse13 smiles with approval).
The bottom line is that a case can be made for open and integrated systems based on requirements. For example, if I want to setup kiosks, more than likely I'm going to want to ghost images, thus, standardize hardware and minimize the physical size of the unit. An additional element is that you will have minimal costs educating your support staff in relation to deploying open systems. This is simply because with open systems, the chances of different hardware showing up in each unit (either upfront or over time) is very high. Having to teach helpdesk level 1 donkeys how to support a wide array of hardware is a daunting task (trust me).
Anyway, I can't see open systems drying up as long as techies and entusiasts are around. I know that at home all of my boxes are open (that is all I will buy) while at work, due to standards, etc. many are integrated systems. I know that I'm not alone here. :)