Rasmus,
Good questions. I'll respond in order.
You said:
"I want both deployment and licensing managed centrally. The users should just see that version 8 has been installed on their computers without any licensing fuss and without having to do anything to get it installed."
==> Given this you want to use an advanced method that allows you to make the e-license download process silent (i.e., invisible to the end-user). You have two options: Adobe-hosted with custom options or in-house (installing a local license server).
Your second question: e-license reuse.
If you reinstall Acrobat 8 Standard on top of what you previously had, then the e-license will be reused. Same is true if you reinstall the OS. However, if you re-image the whole machine, all of your data will be lost, including your e-license. In this case, Adobe has establish a process where you'll get any number of lost e-licenses reestablished in your pool by calling Adobe customer service. Future enhancements we're considering would allow for automatic reconfiguration, but we're not there yet.
Related to you last paragraph:
The licensing model that Adobe sells is per seat, which means that the license is intended to stay on a machine. Users download an e-license from the pool you designate (hosted at Adobe or in-house) and after that, the do not need to connect again to the network. If the user does not need to application anymore, he or she can uninstall the application and return the e-license or return the e-license manually (via the help menu within the application).
Regards,
Juan-Carlos