How useful is it to join ETS My Credentials Vault?

It's a hassle to ask your professors to mail the LOR's every single time. This seems like a great solution. Has anybody here used it? Do schools find it acceptable?

I can't speak for the ETS' thing, but with so many schools using online systems the hassle is small. And any good student knows to have per-addressed stamped envelopes ready for any snail mail systems.