I do HIIT sprints and box jumps with mine, without any issue (never had issues with my X2s, either). The control button area is a little heavier than it was with the X2s, so I did have to adjust the wires to fit more snugly behind my head. That way, it doesn't bounce around and move out of my ears at all. Otherwise, the fit is the same as it was with the X2s, just more streamlined in size.
I don't think outside noise is an issue at all. They aren't noise-cancelling, per se, but I am completely able to get lost in my world with them in. The MySound app allowed me to increase the bass and adjust the other sound settings, so they are more in line with how I like to hear my music. If anything, they might be a little better than X2s at blocking ambient noise.