I worked professionally performing car diagnostics for a little while, so I guess you could say my expectations were really high to begin with. I don't have any complaints and so far I've used it for three different vehicles (two Fords and a Toyota). It's intuitive if you have some experience with diagnostics, but the instructions are very brief, so if you get this, you might want someone a little more knowledgeable to help you navigate it.
I didn't compare it to any other tools at the same time, but it did read an engine code on one vehicle that I was expecting, along with showing ignition count since last DTC on another vehicle, and that number was about what I expected
Functionality wise, it's great; it reads DTCs pretty quick, and if there is a code, gives a short description of the issue. Also shows Live Data, which can be a great resource if you're troubleshooting something that doesn't throw a code (like why your AC isn't as cold as it should be).
Only reason for not doing 5/5 stars is because I'm used to advanced diagnostics and this device made me feel very limited (for personal use, I think this device is perfectly fine).