I pay a lot of attention to optimization. Too many projects I had to work on were bloated with thousand lines of CSS, reloaded the whole page for every user action and used just too much libs and huge frameworks for simple tasks. While this development style may be somewhat faster at start, it always ends up the same : an unmaintainable, slow application. I like the opposite approach, which means using only a few libs, doing the CSS by hand, using frameworks only if they bring real added value. I've had quite much success with this approach, and hope keep working that way for the next projects.
Small details are often what makes an application enjoyable or not for them. Is the page content clearly organized ? Does the user has easy ways to navigate ? Are the loading times fast ? Does the design looks attractive ?
While coding something is achievable by a lot of people by following some tutorials, making the right technical choices and software architecture requires experience. Taking enough time to think about languages, frameworks, data and file structure will help to make a solid, scalable and maintainable application.