I have extensive experience growing and nurturing UX within organizations and building UX teams. The most successful companies that I have built have *always* had a strong UX role in them. I view this position as critical to launching a killer product.
UX is best done by applying a Behavior-Structure-Presentation triangle (see diagram above) to the team or skills required to launch a product. It is a multi-disciplinary approach. Behavior is responsible for the code and various engines that drive the product (think flow diagrams and functionality lists). This can be driven by engineers who know design and production like the back of their hand. Presentation can be handled by designers who know engineering and efficient production of assets, mockups, and wireframes. Structure is handled by “Producers” (a dated term, which really is now more like a Product Manager,Information Architect, Copy Editor, or HTML production jockey) and relies on these people understanding design and engineering intuitively.
Finding the one person with these skills is possible but very hard to find. People like Jaime Russell, Chris “freeform” Miller, Jeff Veen, and Mike Kuniasvky are the gold standard in this type of situation. Check out Mike’s books on UX. Quite good.
UX is best applied as a framework. Startups need to leverage multiple types of expertise in individual people where larger companies can easier afford to acquire this role in one person. If you can find a well-balanced UX person who is strong in the above 3 dimensions (Behavior, Structure, Presentation), you are good to go.