Things I liked: The gun is light weight, and does seem to point fairly quickly and naturally. It is very easy to cock, in my opinion. Once the initial dieseling subsided, the gun is fairly quiet. The most important thing to be liked is the fact that it is a shotgun, by design. I didn't notice any excessive vibration or spring noise as some of the reviewers experienced.
Things I would have changed: Based on how easy it is to cock, I would have used a more powerful spring. With the individual pellets from the shot shells being so small/light, they need all the velocity they can get to have a decent level of penetrating energy at the target. I too believe Gamo should use their Extreme power plant for this gun. After reading some other reviews, I too was sure I could reload the shells. As it turns out, this can be done, but the reloaded shells do not perform as well as the factory loaded shells in regards to velocity. Velocity of the factory shells, which I found to contain between 16 and 20 pieces of #9 shot, averaged about 650-670 FPS on my chrono. To reload these shells, I used a safety razor to slice a .22 felt cleaning pellet into a 3/4 and 1/4 ratio. I used the 3/4 slice for the pusher wad, and the thinner 1/4 slice for the overwad. While these patterened nicely (10 inches at 30 feet), their velocity was only about 440 FPS with the same number of pellets as the factory load. Not taking into account the potentially slight increase in weight of the felt pellets over Gamo's plastic wads, my guess is that the Gamo shells were engineered not to release their payload until the piston had developed peak pressure, to maximize the power plant efficiency. By looking into a new and fired shell, evidence of this can be seen in its design. There is a retaining ring/overwad which is snapped into a receiving groove on the inside of the shell. This would not allow the shot column to move until sufficient pressure had developed to "break" it free. Using the felt wads, I loaded some shells with up to 32 pieces of #9 shot, which produced nice dense patterns, but the velocity drops to below 300 FPS with such a load. I also experimented with card board wads, with similar reduced velocity performance. If Gamo would use the Extreme power plant, and increase the pellet payload to at least 30 pellets while keeping 650 FPS, I would definitely buy it. A gas ram power plant would be ideal, since you could sit and wait for game without worrying about setting the spring, like when you're waiting for rats to come out from under the chicken coop. As the shells are already long enough to carry the extra pellets, there wouldn't be a whole lot of engineering or re-tooling involved for this. Gamo, are you listening?
What others should know: The shells are too expensive to have the kind of fun the gun can provide, even at its current performance level. If you're just jump-shooting grasshoppers, mice, or small sparrows, then the reloaded shells will likely work and will drastically reduce the cost of shooting. But for shooting "big" game (chipmunk, maximum), it seems you will still need to use the factory shells. Ten yards is the farthest you should expect to take a small bird, even then there is some luck involved. For what it is, it's borderline whether or not its worth the money, just don't expect too much of it. My accuracy rating is for the pattern size and velocity - about as advertised but not overly impressive. If they come out with an improved version, as described above, then I'd say go for it.
Things I liked: I had a P1 years ago, but sold it. I missed it, and finally decided to get another. As before, I like that it more-or-less looks like you would expect a pistol to look, and not like a rifle with the stock and barrel cut down. Mostly tho, the relative high level of power achieved with a single cocking motion without any need for CO2 or compressed air is what I like. All you need is the pistol and some pellets. It is a very accurate pistol too, but it does make you work for this accuracy. It doesn't forgive you if you aren't consistent. My pistol seems to like Lasers the best (.177), which is OK with me because they are relatively light/fast. They are averaging about 580 FPS from my pistol (at 6.9 gr each I think). With a very loose isosceles hold, in which the weight of the pistol is completely carried by my non-shooting hand (left hand), I've improved to the point where I can group about 3/4 inch at 30 feet. While that's not great, I seem to have better luck hitting objects. At 30 yards, I can hit a tuna can about 1 in 4, and get very close the other 3 times. I mostly bought it for plinking anyway.
Things I would have changed: These newer P1's come with fiber-optic sights now. They don't look very good, but I admit they do show up well against darker backgrounds. However, the front sight is still very thick/wide, and when you're shooting at smaller targets, it is difficult to center the front sight under the bullseye. If the front sight were solid (the blade is carved-out in the middle to accommodate the fiber insert), I would file it into a thinner blade, but it's not practical to do with so much metal already missing. Even tho they show up well in low-light conditions, I would make the fiber sights an option, not standard. Also, it would be nice if the price were lower, but until a Chinese copy comes out, I don't expect this to happen.
What others should know: My first P1 did have a problem with the rear sight retention pin working loose, but so far this one is staying together. Don't be discouraged too soon if you have a hard time hitting with it. Develop a loose, but consistent, hold, and follow-thru with every shot. I'm giving it a 4 for accuracy only because of it's temperament regarding consistency.