If the GPU speed affects web rendering or phone UI performance (or like JohnH said, photo/video editing, or basically anything that can be accelerated by GPU), those "turbo" clock definitely would help. Actually, look at it this way, those sustained performance probably only benefit gaming. Thus people that don't game can benefit from the "turbo" clock.
Anyway, about the thermal throttling.. I used to disable it on my LG phone, but in the end I choose to enable it because sometimes when on charger it can actually stop charging because the phone overheat! With it off, the phone can definitely get very hot... very very hot. Maybe the SoC can take the heat, but I'm not sure the other components can take it, especially in continuous manner.