I haven't been too impressed with the Chups I have owned so far. I'm not sure if it's the particular blend that I got or what but they are falling apart to put it simply. They don't hold up to the washing machine (possibly due in part to the aggressive american machines), hard to put on over the heel as others have mentioned, holes are forming in the heels, threads are sticking out and coming apart everywhere, they don't hold their shape at the top and get loose after minutes of putting them on and I get the dreaded socks sliding down to the ankle thing going on. I don't know, I might try another pair as maybe it's just the particular blend that I got.
I prefer the Thunders Love over the Chups but the Chups do have the best designs IMO.