I haven't fired it yet; still deer season here. It is very fast and it lets me aim without glasses, which I cannot do with a peep.
The sight is a first-generation Fastfire, which means it's not totally waterproof, and it must be removed from the base to change the battery. The batteries last a very long time though, as long as you replace the cover when not in use. The latest model is waterproof and lets you change the battery with the sight on the gun. It also has 3 brightness settings in addition to the auto mode. A low setting can make the dot look smaller, allowing finer aiming. A low power scope will let you aim finer, but is heavier and probably slower. I may end up using both, depending on what I'm shootin' at.
For someone with old eyes, the Fastfire is better than a peep, I think, and is still very light and rugged. In addition, It mounts directly to the Ruger dovetail with the proper base adapter, the only one that does so to my knowledge. You can get the Fastfire III on Amazon for about $210, with a Weaver/picatinny adapter and the Ruger adapter is about $40. Be sure you order the 3-minute dot, not the 8.
