The new Slingbox Tuner is basically an improved original Slingbox. It plugs directly into your cable or antenna and that is it. You cannot control any other AV components like the new Slingbox AV or Slingbox Pro.
The new Slingbox Tuner benefits also from the improved Slingstream technology. The guys over at Gizmodo, who had already the new Slingboxes for testing, say that the new better quality video streaming technology also wants more bandwidth.
The Slingbox Tuner is supposed to have the same MSRP as the Slingbox AV. Amazon.com has the Tuner listed, but you cannot pre-order it yet. The Slingbox AV is available for purchase at a reduced price on Amazon.com.
See also the Sling Media site.