I like the simplicity of WDT.io and the fact that it offers a free plan.It is very easy to set up. The free plan covers all the essential features and has a free trial period. I have used it for monitoring few of my servers. I dont like the UI as it is not as user friendly as other monitoring tools. I would suggest using this as a free trial and then go for the paid plan. It is very easy to monitor the server and the performance. I like that you can configure rules to monitor your environment with one click (and also in case of errors, there are a lot of options). The price is a bit of a con, but also there's no way to get support from them. It takes some time to set up, but once you do have everything configured properly you see immediate results. We use WDT in our development workstation, and we were able to quickly detect issues in our code base and solve problems before they became critical.