The mac version of Steam is finally out today months after it was first announced.
Portal is the first Valve game to be released as a free download until May 24th and a new set of games will be released on subsequent Wednesdays.
The first games will also enable users to get a glimpse of “Steam Play” which will let them buy a game once and play it on both platforms supported by Steam.
The only noticeable difference between the mac and the Windows client is the position of the window controls. Everything else is pretty much the same for both platform clients.