1. Yes, you can use the same key on several computers. Just make sure you use the file key to activate the others, so you don't use up all your yearly restores. The file works for 14 days I think. Just copy it (or access it on a server) and double click it to activate other installations.
2. Lots of things have been fixed regarding the Client/Server model now. Both images, Video and Music should work just file with a shared library on a server. I think you'll save your self a lot of trouble by doing this, instead of adding several local libraries. Even though you access the same files on a server. When you connect to the server you should see the same play counter, same last played dates etc. There will not be any differentiating the clients as I know. This is because there is no system yet, to access the servers as different users or clients. When using this server function you also get other cool possibilities like streaming to Android phones, zone control and playback possibilities from web interface (and/or Android phone)?
There is obviously a long time since I've used the server model, but I'll start using it soon my self. I think it gives you a lot of advantages.
