Yes I am currently on track for my personal Insanity speed-run record in a 100% playthrough. You have no idea how OP the Bonus Power "Flare" is. It rips shit apart in a 10 meter radius. I have currently +70% power damage and Flare rips shit apart. It has a 5 sec cool-down time for me and with Adrenaline Rush I can even use it for free.
I never had so much fun in Mass Effect than with this build.
Edit: If you are asking why I am not playing an Adept with Flare I have to say that the Soldier has a lot of weapon damage too which is kinda handy as it means that you can do a lot of weapon damage and still quickly kill anything with Flare.
Power damage does also increase the damage of the Ammo powers which is extremely good. My Biotic Soldier rules !!