Where are we now?
X.509v1 has been further developed to X.509v3 within ISO meanwhile, in order the overcome the known weaknesses.
X.509v3 is the basis of the IETF PKIX working group which is aiming at developing a general purpose public key certification infrastructure for the Internet; other standards refer to X.509v3 as well, e.g. SET
There is a new proposal in the IETF for an Internet-certificate (SPKI) - simple to understand and implement (claim) - attribute-based rather than identity-bases - no ASN.1