Is the OpenPGP model still useful?

[Robert J. Hansen]

> So far, OTR adoption seems unjustifiable, really. I mean, it uses the
> Diffie-Hellman key exchange method with block ciphers.

Why is this a problem?

> As of what I got from your (Robert) explanation plus some preliminary
> conclusions of my studies, making use of asymmetric algos with OpenPGP
> would be more coherent and secure, mathematically. Is it correct?

"Coherent" and "secure" are in the eyes of the beholder.  Your statement
doesn't lend itself to a "yes, you're right" or a "no, you're wrong" answer
-- it's just not something I can answer.  Coherency and security are
matters of personal taste and policy.