You can do it and it has benefits like easy editing and placements of objects also custom design breaking the traditional box model. Further more animations are easy to create. And to address your question about fixed content, you can use height/width documents settings and the pinning tools.
My personal opinion is that Hype can be used for small pages, portfolios and/or landing pages as a development environment. If it should be bigger site your better off using regular development tools specially for the task of building pages (maybe even with pre made blocks and rows) and inserting Hype elements where needed. Only my personal opinion!
There are some great examples of pages built with or enhanced with Hype in the #template-gallery and #share-your-work sections.
Hope this helps.