I watched the beginning of my 720p copy of New Order (season 8 opener) sourced from SkyOne. The recap of Lost City (season 7 finale) has effects and 'characters just talking' shots that look SD but with much greater picture quality than the clip of the Abydos pyramid blowing up from Full Circle in the opening credits. But the SG-13 being attacked shot from Heroes in the opening credits looks HD (which does have effects in it). Slightly confused about Season 7 potentially being in HD at this point.
Complicating matters is SyFy airing SG-1 episodes available in HD only in SD along with no iTunes releases of HD SG-1 episodes (although season 10 may have been available from iTunes at some point -- WEB-DLs of those episodes have emerged onto the "scene").