According to the specs, the Slingbox Pro-HD streams in 1080i when given an HD component input.
I've also noticed that the stream maxes out at just over 8000kbps on the LAN or when you have a fast enough Internet connection.
What I'm disappointed with is that at these supposed optimum conditions, the picture sharpness and overall smoothness when viewed on an HD TV is still noticeably inferior to the same 1080i signal viewed directly from the satellite box on the TV.
i wondered if this was an artifact of the Slingbox/Slingplayer having to re-encode and then decode an already-decoded stream so as an experiment, I used my Hauppauge HDPVR to encode the component output of my satellite box at 5mbs and then viewed the stream procuded using the VLC application and displayed it on my HD TV. I discovered that the picture sharpness was noticeably superior to what the Slingbox Pro-HD encode/decode produces and looked much more like HD.
Therefore, I would like to see Sling make improvements either via new Slingbox hardware or maybe it can be done with firmware to produce better quality HD results in high bandwidth environments.