I purchased these on impulse when Amazon had them as the "Deal of The Day."  These "shoes" aren't at all good for running as they slip on the foot and just are not comfortable.  They become sweaty and very cumbersome.  Moreover, these don't provide any lateral stability when used in the gym.  If you have ankle problems these clearly will not be comfortable. There is absolutely no cushioning.  The sole is made of a hard compound which looks and feels like thick rubber.

I'm a size 10 1/2 D in normal shoes and ordered a size 11.  They are a little snug in length, but are fine in width.  They do stretch and conform to the foot just enough to not be uncomfortable, however.  That is, they are a little forgiving if the size you order is a tad bit small.  I recommend ordering at least one half to one size larger than your normal size.  As of March 2012, these only come in whole sizes - making it difficult to find the sweet spot in individual sizing.  It would be nice if these were made in half sizes.

I echo what the previous reviewer notes: the "shoes" do not grip well so I would not recommend wearing these for traction on a rainy day or for rock climbing.  I feel there are better brands out there just by reading the user reviews; however, these are comfortable for casual wear to the beach, a pool where if you are not concerned about slipping, for yoga or just around town if you want people to stare at  the person (you) wearing the funny "things" on their feet.

For $29 I'll keep these handy for (I don't know what yet), but am not blown-away impressed.