Recs.
Updated
Express is a minimal and flexible node.js web application framework, providing a robust set of features for building single and multi-page, and hybrid web applications.
SpecsUpdate
Pros
Pro Good Oauth/Facebook integration with connect module
You can easily add oAuth integration/social logins to your next web app without much hassle, using this authentication middleware for connect.
Pro Express.js is in the Node.js Foundation Incubator Program
Node.js Foundation
Announcement here
The Node.js Foundation is a Collaborative Project at The Linux Foundation. Linux Foundation Collaborative Projects are independently funded software projects that harness the power of collaborative development to fuel innovation across industries and ecosystems.
Cons
Con No single recommended way of doing something
Express considers itself to be a "minimalistic unopinionated framework", it basically lets the developer determine how their project will be organized. On one hand, this gives anyone terrific power and flexibility to use any library they want for a certain task and to organize their project structure however they want. But on the other hand, there's no single recommended way of organizing things, which can be a trap for beginners and experienced developers alike and result in unmaintainable projects.
Con Working with relational databases can be a hassle
Not only express, but every Node framework has this problem. While there exist plugins and libraries that allow developers to use relational databases in their web applications, they are not very good and usually it's a hassle and more trouble than it's worth to use a relational database with Node and express.