Having most of your damage come from the flame explosions rather than the weapon itself meant that enemies with substantial shields/barriers took too long to take down because incendiary ammo doesn't work on shields.
The GPR was great at burninating things, but it had one large flaw-the base weapon dps was bad. But after playing with it a while I wasn't quite happy with it. A while back I posted about abusing incendiary explosive ammo with the soldier, and I settled on the Geth Pulse Rifle as the weapon of choice.
