I ran into an interesting predicament when upgrading our environment to 10.7 (from 10.6.2). Our environment has the main install and three additional polling engines. The initial installations went fine on the main and additional polling engines. However, when I went to the site, I noticed that even though services on the additional pollers were up, they were not polling. I contacted support and they were able to fix the issue.
What happened was that even though the services were showing up, the plugins associated with them were not running. Support ran permission checker and repaired permissions then re-ran the npm configuration wizard (using the repair feature). They repeated this for all of our additional polling engines This happened on all of our polling engines. We are now up and functional, but I thought that I would share my upgrading experience.