Beta vs Release

First I'm glad to hear that you got it and I hope you'll have hours of fun playing it. For that bug you will probably have to wait to Maxpowers or another mac user to help. Just remember, this is beta for a reason.

I'm not sure, but the fullscreen mode currently being used by the game engine isn't the "traditional" full screen mode people are used to,
It is a borderless window maximized to fill the entire desktop.
this is because the game will support multi windows, and instead of uber writing their own Window manager code they intend to use the operating systems built in window manager to handle this which is more efficient and easier to implement.
there is a thread on the topic of why PA uses this fullscreen style i can link to it if you wish.

this means the devs may need to adjust some code in the engine to scale the window to the correct size on macs, it may be a global issue or just one specific to osx 10.9, i will get more info on it and let you know a.s.a.p

Mac OS has always had weird windowing modes so that is probably why it is misbehaving, though I'm sure it is a temporary bug.

If you really want fullscreen now, try installing a windows OS on your mac. I'm sure there are a lot of experienced Mac users here who could help with that if you wished to take that route.

ok that makes sense. It can fill the entire screen except the bottom section where the app bar is. For the time being this is fine.

autohide app bar/dock will fix that issue maybe,
are you talking about the mac's dock??

Should I post my first 2 game experiences here or in the beta section?

Yes, the Mac dock.

im sure that will fix the issue, its because the dock when not in auto hide mode owns that area of screen as an always on top item, that part of the screen stays reserved.

with auto hide on it should fill the whole screen .. like safari in windowed mode maximized

id say post in game experiences and other topics in the beta or backers lounge.

also a good place to post suggestions and ideas for debates with the dev's and community.
The game is being made by fans of the genre for the fans of the genre so all input counts