Slingbox, like many such devices, had no chance as a stand-alone. It needs a distribution channel – it needs to be built in to some other product and just “be there” already and not be something people have to go out and get. Now with this partnership, Slingbox can just be there already for Dish subscribers.
I’m still not sure that this kind “place shifting” will ever move very far toward mainstream customers,. but now it has a chance to go deeper at least. As someone else recently noted, it probably also has a limited “window of opportunity” as all the other forms of accessing content keep getting better (Youtube et al).