Read some of the comments.

* Silverlight doesn't run on PPC Macs

* lots of video quality issues: poor picture, blockiness

* lots of audio syncing issues: audio is several seconds behind on many videos

* can't revert back to the old player once you "upgrade" and most customers are saying that they were conned into "upgrading" by Netflix.

Finally, this all started in November of 2008 and comments are still pouring in and it's March of 2009.