Here are my thoughts.
Surefire tends to make excellent products. I own several of them. In every case I think it is safe to say that you pay a huge premium for the name.
That is a nifty little light. I like most everything about it that I can see in the images and assume it has a good beam. That is going to be a hot light and I would question the 1.25 hour run time if it can run at 300 lumens for 1.25 hours straight. Maybe it can, and if so, that is terrific.
20 years ago, we were identifying targets at that range with 60, 80 and 100 lumen lights and people debated whether or not you really needed 100 lumens of light. Me, I like the extra light. The smaller the reflector cone, it seems, the harder it becomes to project the light farther. With a light that small, 75-100 yards may be pushing its limits.
If you want an accessory on your rifle and the difference of 3 or 5 ounces is the deciding point for what you can add to the rifle, then maybe your rifle is way too heavy for you already. Nobody ever seems to want a heavier rifle, I get it, but small amounts of weight should not be a critical factor.
It may be very uncool to try to be identifying targets with a light on a weapon. Yes, you can often use the splash of the light to identifying targets without aiming directly at them, but for things in the back yard at distance (stated intended use), maybe just a good old flashlight is what you need for seeing what is in your back yard out to 75 yards.
I agree with herrwalther's statement. If you think it is worth that much money to you (and you can afford it), then go for it.