It depends on how heavy you are, but they do for the most part. I think Liberator actually states on their site how much certain shapes can hold before being crushed. As for being helpful, they definitely are.

Yeah, it does support. Some of the shapes support better than others, but most do a bit of support. If you are of a larger body weight, go with the foam shapes (Liberator) instead of the air/inflatable shapes. Less-weighty-people can usually use the inflatable ones okay, but the foam ones definitely hold up better.

all of what's been said already! i've heard great things about liberator, and their products seem really comprehensive when looking at their site.

i'm a very slim person and i actually prefer foam to inflatables myself!! it was brought up earlier in the context of not supporting too much weight, but inflatable pieces also felt really uncomfortable to me in areas where i'm bony.