I work at a company where we hire people for exactly that kind of gig, with a heavy focus on building prototypes of your designs that are actually usable because that's the only viable way to design interfaces. Here's feedback as to why I'm not sending this website to my studio lead to schedule a phone screen with the designer:
1) reused assets from other companies (big no no, even for just a mockup) that are inconsistent with the overall visual style of the project
2) very implausible interactions that were clearly not prototyped (eg the 6 finger pinch... what?!)
3) work heavily inspired from other research projects and designs (10 GUI, various tiling window managers, etc) without showing a clear unifying interaction model. This is more of a patchwork of loosely related ideas, and to me doesn't show clear, deep understanding of prior work (both academic and commercial) in the covered areas.
4) awkward copy that jumps from marketing-style speak to explaining interactions from an analytical point of view. This is the most minor of all points but just hurts the polish of the piece.
So this tells me that the candidate is not a strong graphic designer, not a strong prototyper, nor a strong researcher. He's looking for an internship so only one of the three with promises in the other two would be sufficient, but that's not apparent enough to me here.
Hope that's constructive - I see a fair number of such portfolios/resumes every month.
EDIT: lots of hate on my comment below. The main point seems to be "well you're not totally wrong, but he's a 21 year old intern". Sure, although that doesn't change any of my feedback. I am assessing the work as it stands on its own merits, independently of the designer's age. There is certain work on which 21 year old interns don't have a lot to contribute on, such as redesigning entire OS user interfaces. When it comes to assessing a designer's skills, I prefer to see a series of small, focused pieces rather than one large, sprawling one (the latter is much harder to pull of well unless you have tons of experience). I'm looking forward to looking at how his work has evolved a few years from now.