Personally I find a cleat invaliable for careful trim of other controls with a limited use attitude.... but I am not winning a lot of regattas. : )
When I am in heavy weather and pumpng the main (I do not like to use the traveller up wind) I can only pull in as hard as I can..doesn't matter what the loads are.

One of my favourite boom sheeting arrangements is on the Windrush 14. The mains blocks exit up to a rachet on the boom only 18 inches from the rear attachment point. The business end of the main is always hanging waiting if you have lost it and it is easy to get around and sheet never dogknots. I believe Ronstan now make a swivelling cleat for exactly this style.

Having said these things I am very clear that different trim set ups work for different people and that less fidgeting makes for more speed.