We use DigiCert. They are generally good. There was one case when they started pulling a Comodo thing on us - the lawyer's signature was unintelligible, go and

We use DigiCert. They are generally good. There was one case when they started pulling a Comodo thing on us - the lawyer's signature was unintelligible, go and redo the paper - for some secondary document. But each email includes a note to email their support head if something's off, which is what we did and he had the cert issued in an hour after that. So the tops do care about their service levels and there's an easy way to escalate issues.