My beef with the 1/5th throttle insert is that I like to do wheelies. Maybe I'm wrong, but I don't wan't a touchier throttle when I've got $10k below me on one wheel going 100mph. -1 for the 1/5th throttle insert. This is the same b.s. that people push with regards to short shifters in cars. I mean c'mon. Shortening the throw by a 1/2 inch may take .02 of a second off your shift. When you factor in the clutch in, shift, then releasing the clutch...it's really not signifigant at all for the money. At least in the car, a shortshifter has a benefit. All a 1/5th throttle insert does is make the bike more sensitive to throttle input, potentially in a negative way.
I can go WOT on a 1/4th throttle in about a tenth of a second. In other words .1 seconds. Using Math, You can go WOT on a 1/5 throttle in .08 seconds. So, You get to WOT .02 seconds sooner. A TRE aids the power feeding in sooner by much more than .02 seconds.