I also think that it's not a problem, just an extra challenge.
I generally don't try to avoid turns, so for me, "100% belt speed" is the speed that of a belt with a turn in it. From that perspective, there is no punishment from turns, only a bonus from avoiding turns (which is no different from getting a bonus for upgrading to faster belts).
Faster Belt Corners
Re: Faster Belt Corners
Likewise Ido not believe this to be a problem.
Problem would've been if it severely nerfed belt throughput.
Not to mention use of faster belts for corners effectively solves the issue leaving only blue belts. These would need belt buffering for corners or be used only in straight lines. Both strategies are quite possible to achieve (i've made factories where iron/copper was delivered everywhere through only two straight as an arrow belts across the entire factory.
Problem would've been if it severely nerfed belt throughput.
Not to mention use of faster belts for corners effectively solves the issue leaving only blue belts. These would need belt buffering for corners or be used only in straight lines. Both strategies are quite possible to achieve (i've made factories where iron/copper was delivered everywhere through only two straight as an arrow belts across the entire factory.