Waiting for Sling Player for the Mac has been a trying experience. See my post here:
Do Not Do Dumb Things to Your Customers

In summary:

• First announced June 2005
• First scheduled for Q2 2006
• Delayed to Q3 2006
• Shipped New products with Mac Logo on the Box, but no actual Mac software in the box
• Delayed to Q4 2006

Since then, the company has made great strides:
Sling Makes Amends

Communication has improved and they seem commited to releasing a public beta this month.
Let's hope they follow through.