I know node.js can build web apps that run super fast, but I just can't find enough info about how it would perform in a magazine or news style website. I know some CMS's like Joomla or Drupal (or even wordpress) are very good at it, but as the number of users grow, I'm seeing some performance issues. Naturally, the web server count but as I want to host it in the cloud, I guess working with node and just create a simple CMS based on it would suit the needs for a better user experience once many users can log in and do their social stuff parallel to the main side of the site that is just a news and reviews site. Does any node.js coder knows about it?
I think this question is quite subjective, as the performance of any application written using modern and maintained languages will depend mostly on the skills of the developer(s), and if your website reaches a certain scale it will not depend only on the language but also on the architecture of your distributed system.
Some of the usual strengths of node are that it is event driven, single language for front-end, back-end thus developer integration should be easier. It's event-driven model gives it a nice and easy(subjective!) way to write and understand (for new devs) applications that make heavy use of concurrent operations such as data-intensive operation across distributed systems.
Agree that this is rather subjective, but that said having some experience with node I don't know that there is any particular advantage to using it in this instance. I think frameworks like Django (Python) and Rails (Ruby) are more or less built to accomodate this type of use-case and assuming you have PHP experience but not a lot of node experience, would likely be easier for you to build and deploy a working CMS with very quickly.
Based on what you've described I don't know that any of the advantages of using node will be particularly relevant, and it's unlikely that using node instead of any other modern framework and web server will have a huge impact on your site's performance.