I bought one in April of 2016, which I guess was S0 or S1. In November, I upgraded to an S3. The differences that matter to me: * It's MUCH faster. * Battery

I bought one in April of 2016, which I guess was S0 or S1. In November, I upgraded to an S3. The differences that matter to me: * It's MUCH faster. * Battery life is substantially improved. If I forgot to charge my old one, it would run down during day 2. This one can go 2 days with no problem. * It's actually waterproof. * Cell connectivity is surprisingly useful.