Most of the complaints with Origin are with EA and DRM. I've used Origin for other games and don't really have a problem with it. Some people use it as an excuse to pirate the game though.
The Mac version will be out this spring.
As far as trading, I haven't gotten all the details, however the games you create have a number of towns in a region. There are also Great Works. Not sure yet how those are used.
You can take over 1 or all of the towns in a region. Towns will have resources like coal, ore or oil, and you can build mines or oil rigs to gather those resources. You build depots and it looks like there are some higher level trade buildings (more storage? Not sure yet).
If you don't have the resources, you can buy them on the world market. I think that includes all towns in existence, though I really haven't studied the dynamic yet.
Certain buildings use those resources, so if you're mining it you can use it or sell it on the world market.
Had fun in the Blue Barchetta - Imperial Blue Metallic 2010 Camaro SS/RS with Ground Effects, Beige Interior, 6speed Manual.
I fire up the willing engine, responding with a roar. Tires spitting gravel I commit my weekly crime.