Twisted creates confusing, bloated code.

Every time you have to do asynchronous work, you have to mentally follow the chain of deferreds to ensure you understand exactly what code will be called at what time. Coupled with its unpythonic, deep hierarchical API, Twisted almost literally twists your code into a jumbled blob.

Unless you need the existing protocol-specific APIs twisted provides, stay far, far away. Find something more lightweight, like this, or Eventlet, or something else that lets your code remain concise and clear.

This comes from my experience writing a Twisted server for my startup, and subsequently rewriting it when the Twisted version became far too difficult and frustrating to maintain.