Marketplace at least in the US has shown that once you have this, the actual cryptography really doesn't matter. All anyone seems to care about seems to be "We are company X and have been doing this business for Y years and here's our standard operating policy. We emailed address A at time T1 and the person reading that email address used our online services to electronically 'sign' the pdf P at time T2."

Everyone trusts Adobe/Dropbox/et al to make that claim, nobody cares about certificates and what not.