Take your primary panel, for example. The only content in this area is your welcome header, a brief line of subtext, and your “Go to Top” button. For the type of site you’ve created here, the expectation would be that this area (which takes up the entire viewport) would have something more.
By ‘more’ I mean a background image… some other snazzy “Hey look at how WOW this is!” element. Instead as a visitor I’m presented some brief somewhat-informative text on a sea of white.
Consider this example of another one-page website: http://tympanus.net/Freebies/Synthetica/
The use of graphical elements against minimal text helps to immerse the viewer and present a level of design that elevates the site as a whole. What you’ve created is functional, but barren… which is why I feel it difficult to critique from a design perspective. All the structure is present – but the UX is missing.