Same here.
I love my X series. The only time it's hard to clip in is when I get new cleats or pedals. A few rides and some lube take care of that. I lube them every 2-3 weeks during the height of the season.
Of course, I almost never stand to pedal. However, if I do stand, like on a little hill, or to stretch, I don't feel unstable at all. I think you just train your feet and legs to get used to the float and after a bit, it feels normal. I know that when I used to go back and forth between my X pedals and SPDs on my Jamis or my mountain bike, I felt like I was "locked in," my knees hurt, and I generally was unhappy.