Big difference? Not if your current set is well-matched for shaft and lie to your game. I did get a 10 yard improvement, but I also went from your shaft to the TT Red AMT metal shafts. The 718 graphite AMT shafts were less than 5 yards better. I originally elected to not upgrade and instead invested in a TPI trainer, but that effected enough change in me to upgrade to the 718's.

Frank,
Just as you do I had 716 APIs with Kuro Kage reg flex shafts. After reading about the Tensi graphite AWT shafts I went to my Titleist fitter and tried the 718s. I liked the idea of the longer shafts being lighter weight and easier to swing especially later in the round. I noticed when I tried them that they seemed more forgiving than my 716s. I have had my 718 AP1s with Tensi graphite shafts for almost a month and a half now and my handicap has gone from 11 to 9. Not bad for an 80 year old. I've had 710, 714, and 716 AP1s. The 718s are more forgiving, longer, and better looking than any of those. One thing that I don't understand is that it's very difficult to hit them way off line. They seem to go relatively straight know matter how bad a swing I put on it. The trajectory is pretty much the same as my 716s and the feel is better.

I just recently switched to Titleist, and I ended up going with the 716's vs the 718's due to the fact that I did not find a noticeable difference in distance/trajectory/etc. And not to mention I saved quite a bit on a new set of 716's vs new set of 718's. That is just me though.

Go to a Titleist Thursday event near you though, and hit them for yourself!