We are happy that we can help, more coming in a short time.
When you add a new domain, or subdomain, you will need to add only for that domain (nginx.conf) the settings. We are working to have this automated in Power Toys, but you can do it easily as well in /skel/0/ .
No reboot requires, only nginx reload.
Yes, it is require to have for each domain. We still study how can we enable only for selective domains, not to all, but it is harder to do that.
Yes, it is stable with Yum Install, we use ART repository and all work fine.
We use also on this server nginx for all domains, the only issue what we have found and we did notfigured yet out why, that on login screens we get rediredted to port 8080, but strange in not all case. phpBB and Cerberus so far with this issue.
All the rest is more then OK.
We have all of our servers in Germany (Hetzner) but we think is fast enough. I know that in US could be faster, but most of our clients are in EU on hosting.
But we have a service to maintain any server with PLESK, anywhere in the world.
See this link.
http://www.grafxsoftware.com/description.php/PLESK -Based-Dedicated-or-VPS-Hosting-Management-Service s/26/