I’ve only recently tried out the RealPlayer and QuickTime alternatives out there. Due to my hosting arrangement, I’m only able to stream Real A/V streams. The server side stuff is actually really nice, so I’m not complaining about that. I realize, however, that there are a lot of people out there that don’t particularly like RealPlayer or QuickTime clients to view their respective formats. The alternatives make use of Windows Media Classic (not sure why they’re not using the latest versions) and work very well. The readme details specify that errors may occur on the more complex streams such as those using RealPlayer’s SMIL scripting.
Link: QuickTime Alt.
Link: RealPlayer Alt.