We have a few of them and my daughter used them for her lunch and was able to open and close (4.5 - 6) them by herself. I did they had some pieces that were different depths but the lids were the same size, so you could mix and match a bit. However, they don't stack so they take up a lot of space in my drawer.
I've had one lock break and I think I have had a few pieces for about two years. So they have lasted a good long time. I tend to handwash them and they don't go in the microwave.