The weight limit is still 45 lbs, but I have boldly exceeded it without incident. I worry about the toll it will take on the trailer in the long run, but it hasn't been an issue yet.
I have no clue what the swing arms were like before. Mine is new so must be the newer version, they don't seem weak, but are nor beefy either.
The only poor handling issues that I've had seem to come from carrying liquid weight. Fully loaded with dry-goods I'm doing 28 mph downhill with no issues whatsoever.