DevExpress can help you create the big web app of your dreams. DevExpress works great with data-centered enterprise-level applications that require the use of enterprise-grade data grids, pivottables, and integrate them with all the widgets like buttons, popups, forms, etc. I would not recommend DevExpress for small apps that require only basic widgets like radio/select boxes, buttons, text boxes, etc. You can get those widgets for free or even make your own.
Angular is our framework of choice for a number of reasons. Business data is almost always displayed in a grid format. It makes sense to start with a strong widget that is powerful and fast when building applications. Ignite UI provides a complete toolset of widgets for other frameworks, but Angular is our focus. Ignite UI is helping us deliver a great UX/UI.
We tried DevExpress when we started a project a couple of years ago. At the time, the documentation and ease of use went to Infragistics. When trying new or updated tools, the documentation and samples are everything. Having minimal documentation or documentation that seems to be written for people that already know how to use the product is just plain frustrating. Samples need to be something close to the real-life usage of the product.