What does the software or service do well? It is to me the best option for remote connecting to a computer. Whether that be a remote connection to your personal computer from any device you install the software on, or for business use to connect with your employees when they're having issues for example. It is simple enough that someone only needs to be able to open the program and give you the requested ID and password to get you connected. This was invaluable when working with remote employees who were not super tech savvy. A previous company I worked for dealt with 90% remote workers, most of them not the most tech knowledgeable. It saved me more time than I'd like to imagine, as limited tech skills meant limited ability to explain tech issues as well. Being able to remote connect to their station, see first hand the situation, tell and show them how to fix an issue, rather than trying to decipher what they're saying and guide them to the best solution you can think of based on what you got out of their description. We also used it for training purposes, several stations could connect to one user and view their screen, hear what they said on our voip service, and get "in person" training by shadowing someone that lived on the other side of the state through TeamViewer. Current company has several display monitors operating off a raspberry pi around the office. They are set to displaying different information from a web app, occasionally the web app bugs and they need to be refreshed or some other simple issue. Rather than having to walk across the office to plug in their adapter and do whatever work needs to be done, they just install a TeamViewer user on it, remotely connect and fix it when it has an issue. Heaven forbid the network goes down though. I even use it to help my Dad with his computer issues. Whenever that "extra search bar is back again" or one of the many fixes needed over the years comes up, I can just remote in, fix the issue, rather than trying to find someone to go fix his computer for me now that we're not a short drive away. It has a long list of beneficial uses and I'm sure many others if you can be creative about it. Having come from a tech background, it really is worth the price to pay for the commercial use licenses.
What does the software or service not do well? The connection requirements can make things a little sluggish depending on what you're trying to do. I don't suggest file transfers over a remote connection, with any software really, there are better options.
What do you wish you had known about the software or service before using? How creative you could be with it's uses. It took a few years coming up with my own ideas and learning a cool thing here and there from different people. Couple hours and a general Google search, you'll find some fun things to do with it.