I did the Great Guns program with another guy at the gym and we both like it and got results.
I went on to the Chest & Back series, and am less impressed with it. I normally do a lot of back work anyway, and I find the workouts leaving me wanting for more back involvement. The shoulder workouts are ok, but the chest work is a real bore. I am nearing the end of week 9, and when I have finished weeks 10-12, I plan to take a week or so off and do Great Guns again.
Then 12 weeks later I want to find a different chest program altogether. If anyone knows of one, let me know.
As for results, I got a lot of favorable comments on my arms toward the end of Great Guns, and I did the program while I was not attempting to bulk. I got stronger and really cut. Next time around I will do a bulk along with it to gain some size.
What I do like about both programs is that the routine keeps changing. The workout tempo changes, and it incorporate supersets, tri-sets, and some movements that I had not done before.
Hope that helps.