I throw a lot of Prodigy. This was the disc that got me into Prodigy. I tried a few of their discs, but it was this M3 that got my attention.  Several years ago, I bought handful of Prodigy discs, including this M3. It's the only one that has stayed in the bag constantly since then. I've played without it, sure, but it always comes back into the rotation. I don't know of another mid that flies or feels like this M3 (or their M4 for that matter). When I first got it, I remember seeing S curves in the flight, but at this point, it doesn't do that anymore- kind of the opposite of a break-in. 

My M3 is 177g 400G X-Out. It's not a domey disc, though at one time it might have been. At this point, it's a puddle top. It's a bullet. Most reviewers have a domey, even flippy M3. This is not that. But it's not an overstable disc, either. When thrown properly (flat and hard) it flies dead straight with very little fade.

Plastic-  My M3 is years old, and has been thrown as much or more than any other disc in my bag. It still looks relatively new- you can tell it's been thrown, but there's nothing that makes it look 'beat'.  It is durable, grippy, and comes out of the hand very comfortably. 

Flight-  This thing is a bullet. It goes straight where you throw it, with much disregard for wind conditions. It likes to be thrown flat, and responds exaggeratedly to hyzer. This is likely due more to the puddle top than mold, but I can't say for sure. When I try to hyzer flip it, it typically comes out early and downward.  It will hold an anny. Virtually No turn, very little fade. It requires power and command to make it work, but it does things that no other disc I have thrown can do. 

Feel-  In the hand the rim is round and somewhat bullet-nosed, so it's comfortable against your palm. It is similar to the M4, which is more bullet-nosed. One thing that separates this from most discs is its rounded, comfortable feel. It feels like it won't fly fast or far, but that's not the case.

Compared to a Comet-  they both can fly straight, but the comet does so with a steady light touch, and this one does it with a firm hand. The comet will become a flippy mid driver when you throw it fast, while this M3 will just fly like a bullet. With a light touch, the M3 will hyzer out. Again, more the puddle top than mold, I think.

I recently picked up a 350 M3 to compare the two. I'm stoked to try it. Because I love me some M3

Got a 170g M3 X-Out in 400g plastic.  The 400g plastic looks and feels great, nice grip to it.  It also throws very well.  It has a good straight flight with some fade at the end.  It will hold hyzer lines well, but I was surprised at how well it held anhyzer lines.  It has been my only mid in minimized bags and it has been very reliable.  It did turn over on me just a bit on full power crank-on-it throws.  All-in-all, I'm pleased with and recommend the M3.