That shaft is the real deal. 100%

Good driver, but it is 4.5 years old technology. Getting fit for a new model will minimize dispersion and maximize distance and the effective size of the sweet spot. But there is that price differential. If you don't need to adjust to fine tune the driver, there are those that will say the 909 D3 is still relevant.

For me, the TS greatly improved me from the 915, but part of that is the shaft and loft selection.. Not to mention having TPI instead of me fitting me for driver.

Still relevant for sure! Titleist makes fantastic equipment year in and year out. The 915 series is awesome and one that is still played on tour by a couple of players. As everyone says and it is true, get fitted. Take that club to a launch monitor and see how it compare to your current club. If it’s better in distance and dispersion it’s a no brainer. Know that the D3 is the smaller 440 vs 460 cc version of the 915 releases and will have lower spin and a little less forgiveness than the D2. You can work it better on drives where you need to move the ball a little. Titleist clubs are great because they do exactly what your swing tells it to do. No gimmicks just performance.

I had the 915 driver with a rogue shaft and loved it. I currently hit the 917 D3 with a speeder tour spec shaft and like it just as much. The diamana shafts are great but I they don't seem to work as well for me when compared to the other two I mentioned above.

I hit this exact set up and have improved greatly from last year to now off the tee box. Brand new? Def still relevant.... I’m team titleist but not really a club snob when it comes to needing the newest technology in my bag at all times.

Still relevant. Bought my 915 new towards the end of their run and still use it today. As long as the shaft works well with your type of swing you shouldn't have any issues.
Technology hasn't made the 915 models obsolete at all. Most gains are minimal at best.

Unless you are chasing yardage the 915 still preforms well. Yes the new models have a couple of more yards pop but I still think it's a very serviceable option.

I play the 917 D3 and it’s great! Don’t have experience with the 915D3 tho. Just remember to get fitted for your driver!