I'm against banning tech trade. As I already said in other post. It is far more important to remember to adjust tech costs according to map size and number of players.
For city trading, I do not think I care that much. In a way it makes sense, opens up lots of possibilites. In other way, it allows some stupid crap, and make alliances (official or otherwise) slightly stronger, by allowing trade of wonders, probably most important being statue of liberty (though if no anarchy is removed from it's effects, it might be allright).
@thegrime about GT7 (I was not there) seems like realistic and expected buisiness, allies helping to recapture cities, nothing fishy.
As for trade routes, one time bonus calculation must be adjusted, to variouos factors to avoid some crap like transport coming in with 8 caravans and generating thousands of gold on the spot. IMO something like 10-20 gold for distance equal to map diagonal length, and remove bonus from different nations (this is just pure bs imo, though I know why it was implemented) and different continents (as this is even worse, get city in some stupid 1x1 island and bam double revenue...). And what I think about permanent trade route output, you probably already know...