I can only confirm this for Windows. Got no Mac ; )...
Ok, odd. It works on windows for me (and it's the first time I've installed it on steam). A few questions:
1) How big did the steam client say the download was for you (on the Library->Downloads screen where it had the progress bar, etc) ?
2) How big does your OS say the "C:\Program Files (x86)\Steam\steamapps\common\Shattered Haven\" (or wherever you have it) folder is?
3) What happens when you try verify-cache on it in steam?
Thanks