Channel 9 videos should play on any browser that supports H.264 MP4 or WebM (IE, Chrome, Firefox, Safari...)
If the video isn't playing, try changing the format. C9 will try to automagically determine what the best format is, but sometimes it takes a human touch. Below the video, click on Format. HTML5 is a good option usually. If you have a C9 Profile, you can change your detail format there too.