Portal on OS X is a lot slower than on Windows

Mac gamers rejoiced after Valve unveiled that Steam was coming to Mac, however, it now seems that while Steam is on Mac, it has taken a massive performance dump in the transition. According to several tests, including at
Tom’s Hardware and
AnandTech, Portal on OS X is up 80% slower on than compared on the windows version, and is on most MacBook laptops, even high end Pros, unplayable at anything but the lowest settings. Hopefully Valve will improve performance in updates.