The P3 prostate massager is, obviously, designed to be used by people with prostates. It's a "put it in a let it do its thing" toy, not a "move it around, or in and out" toy. So the idea is to insert the long bit so that the tip rests against the prostate, turn on the vibrator, and then lie back and enjoy.

That said, many prostate toys double as G-spot toys, and some are even sold as both, often with different (socially approved) colors. I haven't seen a G-spot version of this one, and, not having a G-spot myself, can't test it out that way. But at least one other reviewer has indicated that it's a good G-spot toy. But I'll concentrate on its use as a prostate toy, for the obvious reason.

The P3 is made from a hard, rigid plastic. It feels quite soft to the touch, so much so that you might think you could dent the plastic with a fingernail. But, in fact, there's no give to it at all. Perhaps the softness is really just smoothness, and the toy does feel very smooth, overall.
That said, on the one I have at least, there is a seam that runs down the middle of the entire toy. It's clearly made from two mirror-image pieces that have been joined. I can easily feel the seam with my finger. I have not, however, felt it when inserting the toy, so it's not an issue. But I guess I would prefer if the seam were less prominent.

I'm a bit puzzled by the design of the P3. I'll give you the objective facts first, then explain my confusion when I talk about performance.
Overall, the toy has a T-shape. The vertical part of the T is what you are meant to insert (in my case, into the rectum), so I'll call it the "insertable" part. The horizontal part of the T I'll call the "handle".
The handle is about 5" (12.75cm) long. On one end, there is a small button that controls the vibrator. The other end, I think, is meant to lie against the perineum. This toy is therefore extremely safe for anal use. There is no way you could (accidentally) lose the P3 up your ass.
The insertable part is about 4.5" (11.5cm) long. It is just 1" (2.5cm) wide at the widest point, which is near the tip, and only about 0.5" (1.25cm) near the handle. The small overall dimension should make it easy to insert, even for beginners. The thin part near the base makes it easy to keep in place, once it is inserted; the anus can get a pretty good grip here. There are two "bloops" along the length, both of which bloop up away from the button.
The insertable part connects right at the middle of the handle, but it is not quite at a right-angle to the handle. Rather, it is slightly curved, up away from the button. Most prostate toys have this sort of curve. This one's is pretty gentle.
The vibrator (which is reasonably powerful, but definitely on the louder side), is housed at the very tip of the insertable part. This is a Very Good Thing, because it helps get the vibrations exactly where one wants them to be. There are three different speeds (slow, medium, fast) and two sorts of pulsing vibration patterns: one is just a series of "fast" pulses (on-off, on-off, etc), and a slow-medium-fast pattern. This is a good feature though, nowadays, most toys offer more options.
It runs off a single AAA battery, which is not included. You have to screw off the part where the button is to insert the battery, and then screw it back on. Some reviewers have reported needing to screw it on really hard to get it to work. Mine does not seem to have this problem, but, if yours does, I'd recommend you try using a small screwdriver to raise the two contacts that sit on either side of the battery. I've had to do this with a different toy that had a similar problem.
The P3 is said to be waterproof. There is an O-ring at the bottom of the threads where the cover screws back on, so I'm prepared to believe it. I don't tend to use my toys in water though, so I've not tried this.

I've had enough experience with prostate play that any vibrator that has the vibrating mechanism in the insertable portion (preferably the tip), so that it delivers sufficiently strong vibrations to my prostate, will get me off. The P3 passes that test. But the real question, for me, is: How good a job does a particular toy do as a prostate vibrator specifically?
For a long time, my favorite and most effective prostate vibrator was something akin to this one, which is just your basic plastic phallic vibrator with the vibrating mechanism at the tip. It worked, but it was never easy to get that toy situated properly. To make solid contact with the prostate, you have to insert the vibrator itself at quite a dramatic angle, which meant reaching around behind myself to pull the base of the vibrator towards my back, so that the tip would go towards my belly and so towards my prostate. It's not the most comfortable position.
So, if something advertises itself as intended for prostate play, then I think it needs to be better than my old favorite. In particular, it shouldn't require contortions to get it properly situated. Rather, it should be so designed that, when it's inserted, some appropriate part of the toy comes into nice, solid contact with the prostate and stays there.
Unfortunately, the P3 does not pass this test, not for me, given the way my internal anatomy is laid out. (Your mileage may vary, of course.)
As I said earlier, the design of the P3 confuses me a bit. I take it one is meant to insert it so that it curves up towards the belly and so towards the prostate. That's how almost all such toys are designed: to curve towards the prostate. But if you insert it that way, then the button is on the part of the handle that is "down below", and it can be very hard to get to it. So I've also tried it the other way. If you insert it that way, though, then the toy curves away from the prostate, and there's no way it's going to make firm contact.
But even if I insert it the other way (curve up, button down), the P3 still doesn't make firm contact with my prostate. The basic problem here is that the insertable bit just isn't curved sharply enough. Of course, I can, as with my old favorite, reach back around myself and pull the base toward my back, etc, etc. I can do that with it inserted the other way, too. But that's not only an uncomfortable position, there's supposed to be a part of this toy that stimulates the perineum. But if I pull the toy towards my back, then I pull the alleged perineum-stimulator well away from that part of my body.
The other thing I should mention is that the P3 is very, very loud, even when it is inserted. It would easily be heard through a closed door.
So, overall, I guess I can't say I'm that happy with the P3. I will probably use it from time to time, as I like the two vibration patterns, but, as I said, a prostate vibrator ought to be designed for easy vibration of the prostate. This one just isn't.

I have just used soap and water to clean this toy. The hard plastic does not seem to porous at all, and it doesn't retain any sort of odor (e.g., that from the soap). Since it's waterproof, it wouldn't surprise me if if you could toss it in the dishwasher (top rack!), but I've not tried that and am not necessarily recommending it either.