FT can get 30% more mass to LEO. That is a pretty big performance increase, especially considering that it enables SpaceX to carry the maximum payload of v1.1 in expendable configuration and still land the FT rocket. Even if we assume that half of that performance boost came from the other improvements, 15% is a significant increase.
Shaving just a little weight (especially on the 2nd stage) or squeezing out just a little more performance can have dramatic differences in mass to LEO.
The question is how much this will increase overall operational cost. Up until this year or so, it has seemed that SpaceX has been willing to compromise on performance to get lower overall operational cost and reliability.
I'm a bit worried that they've started to go the other way with some of the improvements they've made this year.