The use of the adverb, here again, standard? Most often on Facebook, I tend to see simply "...plezuro renkonti vin."
Those two sentences mean essentially the same thing, but are expressing it slightly differently (but both correctly). With the adverb it means pretty directly "it is nice to meet you" where the adverb describes the action. With the noun, it means "it is a pleasure to meet you," equating the action with the noun pleasure.
Also, your username is pona. :)
Learning Esperanto has deepened my realization of the extent to which English has suffered attrition since the days of Bunyan—"good to meet you" vs. "well met."
I actually do tend to say "Estas plezuro..." but this way is also perfectly acceptable.
I've also been known to say "Mia plezuro". Shorthand for the above, but emphasizing that the pleasure is all mine.
And you must say it whenever you meet another Esperantist, even if you are not pleased to meet them. :)
What is the typical response to this? "The pleasure is all mine" is what I would say in english. "La plezuro estas tute mian."?
Mi pensas, ke oni dirus, "La plezuro estas tute (la) mia." Vi ne bezonas la akuzativon en tiu cxi okazo.
I think one would say "La plezuro estas tute (la) mia." You don't need the accusative in this case.
Estas is often translated as "it is". One need but ask "what is the it about which I'm speaking" to determine whether to add ĝi, or not. If you can't pin it down with any degree of accuracy, then leave that word off and just use estas.