Angular pipes are great for data transformation. json, async, datetime are some of the largely used built-in pipes. Learn how to make a custom one for your need.
Creating custom elements in Angular and exporting them as web components is real simple. See how I made a custom subscription element in Angular and used it as native HTML element.
In Angular, you can upload a file and at the same time get the progress by enabling the reportProgress flag on HttpRequest object. Source code available in Github.
It's very easy to set up asynchronous validation in Angular Form. You can check whether provided email/date/name etc. already exists in the server with an HTTP call.
updateOn: 'blur' and updateOn: 'submit' are the options we were really craving for while working with Angular Forms. Now it's available out of the box and you don't need any custom implementations.