Being able to add a note on the fly to a "to-do" list or add a needed item to a "grocery" list with ease. It's handy being able to access it from practically anywhere. I often find myself needing to do a task and pulling out my phone to add it to my to-do list.
The iOS app sometimes gets into a state and doesn't update your notes (won't show new notes from other devices / computer), needs to be re-installed to resolve
Your notes take up space in your Google account's quota, though this is not very apparent at first - you have to keep an eye on what you are storing - huge pictures better not go in there
Google Keep is very easy to use. Currently, the company I work for has employees from different age brackets, and this is one of the easiest apps on G-Suite to explain. Not a lot of people use it, but it is due to personal choice since a lot of people still prefer pen and paper to keep their notes.
I gave this rating based on the ease of use, the simple functionality and how well it does at keeping my attention and helping me continue to use it and stay on track. The functionality mentioned before alongside the reminder functions and how it utilizes Google's powerful machine learning tech to better its software is remarkable.
I used to use Evernote before Google Keep, it is an excellent product too but I found it too heavy. At the time (not sure about now) it always wanted to download all your notes onto your device before you can start using it. Google Keep is more a cloud product, so it's lighter on your device, it doesn't download every note you have at once. Also I tended to store a lot of heavy things in Evernote because it seemed to encourage me to do that, like large photos and documents. Google Keep encourages me to focus on text only mostly, though it will take a photo as part of the note as well. I also like Google Keep because it is a part of my Google Account and integrates with other Google products.