I bought two M&Ps about a month ago. A full size 9mm and full size 45ACP. They felt good in my hand at the shop and dry firing at home, but I just didn't care for them at the range. They didn't "lock" into my hand as well as my Glocks (even though they felt better overall), felt somewhat top heavy, and I didn't care for the trigger. I definitely understand why so many people rave about M&Ps. They just aren't the right gun for me.
I never sold my Glocks, I was just willing to try other platforms.
I also did this with some 1911s a few years ago. I got bored with a generic GI style and traded it for an upgraded model that had problems galore. I ended up coming back to the same GI that has been problem free.
After trying tons of different guns, I really like Glocks, 1911s, and Beretta 92/PX4 the best. I guess I'll just stick with them since I seem to shoot them the best.
Has anyone switched from one gun/brand to another, only to come back to the same one you left?