I would like to preface by saying I would give this knife four and a half stars, if the scale worked that way. It is a very good knife indeed. There are just a couple minor issues that stop it from getting a full five stars from me.
This is a knife that is an amazingly good value. I have a variety of higher end knives with titanium frames and S35VN or M390 blade steel, most of them flippers, and most of them a good deal more expensive than this knife. This, functionally, holds up to all of them, and is a better cutting tool than most of them.
The blade geometry is quite good, though it could stand to be a hair thinner at the edge. The lockup is excellent, with no blade play. The blade centers well. It's of sturdy construction. It has a steel lockbar insert that doubles as over-travel protection. This is a major plus to me, as it adds longevity to the lock of the knife, and helps prevent lock stick.
The ergonomics are especially good, and the knife is comfortable in every grip I've tried, without any major hotspots. Using this knife day to day is a joy, and the edge has, so far, help up well to medium hard use. When it comes time to sharpen it, I plan on bringing that secondary bevel higher up on the blade, to get a slightly leaner edge.
But, as I said, there are some issues. The first is the pocket clip it comes with. The clip isn't terribly flexible, and has one point that is incredibly thin. Others have reported that it bent or broke at this point. While I didn't have this issue, it was a big enough problem that Massdrop released a redesigned clip.
The other issue I had is that the lock bar edge is a bit abrupt, and digs into my thumb a bit when unlocking the knife. While this isn't such a big deal with day to day use, you'll end up with a sore thumb in that initial period where you just want to keep playing with the knife, especially with an action this good.
Also, while this doesn't speak to the quality of the blade, Massdrop has demonstrated that they are unwilling to properly support their products. While they released an improved pocket clip, they did so only as a limited time "drop", which has now ended. If you didn't get one? Tough luck. I was only able to get one in the incorrect color, as they'd run out of the popular colors. If they were actually committed to their customers, everyone who'd bought this knife with the original, poorly designed pocket clips, would have gotten the new clip for free. It wouldn't have been sold for an additional $15 in order to make a quick buck.
The simple fact is, this is a great knife being sold by a shady company. Be wary, and I wouldn't expect much in the way of good customer support for your blade if something goes wrong.