Biggest strength would be performance. Biggest weakness would be maturity. I think almost every pro/con I can think of can fall into those 2 buckets right now.
I'm a big fan of type systems so Pony having one is a big win for me.
The maleability of Pony and its immaturity helped us in some ways. We were able to treat it as a runtime for us to help mold and fit to our needs. That wouldn't have been possible with Erlang.
Has there been any progress towards a preemptive scheduler? Otherwise, I'd think that's the most obvious weakness.
I've heard rumor of someone working on a preemptive scheduler. The current cooperative one is about to have runtime backpressure added to it which is going to be a really nice scheduling win.
Pony classes are defined using a "class" keyword. Classes have properties and functions, where functions are like methods that you would find in a language like Java. Pony supports structural subtyping via interfaces and nominal subtyping via traits, and it disallows multiple inheritance.
I'm not sure how much that helps, but if you have more specific questions I'd be happy to try to answer them. I'm a little rusty on my Erlang, but hopefully it will come back to me.
I've worked in Erlang-land far longer than I've lived in any OOP-land, so I'm not sure what you mean by enterprise'y OOP. Coincidentally, Pony's rules for "Packages" are something I just smacked my ignorant head against a few hours ago. The subsections of https://tutorial.ponylang.org/packages/ in the tutorial can probably answer at least some of your question: specifically "Package System" and "Use Statement".
So, does it?
Fields and methods can be public or private. Private is akin to Java's package private.
There are no instance variables.