Pros:
a) If your application does not have any CPU intensive computation, you can build it in Javascript top to bottom, even down to the database level if you use JSON storage object DB like MongoDB.
b) Crawlers receive a full-rendered HTML response, which is far more SEO friendly rather than a single page application or a websockets app run on top of Node.js.
Cons:
a) Any intensive CPU computation will block node.js responsiveness, so a threaded platform is a better approach.
b) Using relational database with Node.js is considered less favourable