Last night, my friend and I started brand new 'cities' in a larger region (our original region only had 1 city space for each of us). We gave the *mostly* residential strategy a try and while you can grow your city-pop really fast that way, we found it is also the single best way to bone your traffic situation really hard since without local commerce and industry they will all try to leave and re-enter your city at the same time.
We have also found that 'regional-trade' doesn't appear to be working properly or I should say consistently (I suspect server issues etc. here). This is pure speculation on my part, but I believe it possible that the regional RCI may be having the same issues the regional trade/gifting etc. is suffering from which is why it sometimes appears like residentials are commuting to 'vapor-jobs', commerce is getting 'magical-freight', and while RCI states there is never enough localindustry there is massive regional job-sharing going on (at least for industry it seems).
Another thing we found curious is the fact that global trade take precedent over regional trade. This does seem odd and counterintuitive at best. Say my town has a massive surplus of something, my friend cannot 'purchase' all of it. Seems like while the 'regional interaction' is supposed to be the focus of the game, in some cases the game engine still makes global choices for you, which isn't desirable in all situations.
I agree with bonscott that the new heavy focus on regional everything opens the door to intentional greifing and actually makes this game much more difficult and frustrating to play by oneself than it needs to be. Even with a friend such as I have been playing with, when we're not on comms he or I can easily make decisions in our city that have far-reaching and sometimes costly consequences for our neighbor.
Like I've said before, perhaps this new game should have been called SimRegion afterall.....
Having said all of this, I do believe the devs will continue to improve on the game. It does seem unfortunate that these days we the customers are more often than not being used as the 'final beta' phase. Oh well.......all large projects (and SimCity 5 is definitely a large project) run the risk of doing that, and I don't think we're going to be getting away from that any time soon!
In any case, my friend and I are still having a ton of fun.......even if that 'fun' sometimes comes with a few expletives hurled at each other for 'hey man.....you just screwed my city......what the %^&%^ did you just do?! " hehe