I like it, but I'm always frustrated by these reports of ideas for grid storage. I don't think I've read one yet that mentions end to end efficiency. Grid storage isn't only about efficiency, but it seems like a reasonable question to ask.
I believe that ultimately, a flow type battery will be used for covering peak demand for power. A flow battery has the advantage of instantaneously converting chemical energy to electrical energy. Some rather large flow batteries already exist using vanadium REDOX technology. Last I heard, there was a 400MW⋅h flow battery being built in California. The advantage of a flow battery is that there are no limits on the number of charge-discharge cycles in addition to the immediate conversion when the need arises.
Why go through the inefficient first step of converting (for example) wind power to electrical power to haul the weight up-hill. It might be more efficient to use the mechanical power haul the weight up-hill then do the mechanical-to-electrical power conversion once when the weight moves down the hill.