It's taken me a week to be able to talk about the series finale, but I find that the end of Stargate SG-1 is just the beginning. I am sorely ticked off that the Jack/Sam relationship storyline wasn't resolved during the ten season run of the show but with Sam taking Dr. Weir's place as commander of the Atlantis expedition perhaps that particular plot point can be resolved during the fourth season of Atlantis.
Another reason for this being the beginning of something is that it opens the series up for more movies. With the entire Ori storyline wrapping up in "The Ark of Truth" and Ba'al getting his just desserts in "Continuum" I can't wait to see what's in store for our intrepid explorers in the future.