I loved SG-1 and thought SG:A was pretty meh. I appreciate what they were trying to do with SGU, they just did it really poorly. The show had a lot of good qualities and
a lot of bad qualities. It was a weird mix. There was the nonsense with the stones, which took up way too much of season 1 (especially the first half.) There was also the power struggle between Rush and Young, which got way out of hand to the point of becoming unbelievable.
Some of the relationships on the show were handled reasonably well, although most of them (like Scott and Chloe) were badly mishandled.
I don't think the show was a total disaster, but on the whole it was pretty damn mediocre, and that just doesn't cut it in today's TV landscape.