The most useful feature is that you can monitor your servers from anywhere in the world, so it's very easy to keep an eye on everything even when working remotely or traveling without having to worry about being disconnected for long periods of time! It also has some nice features such as alerting if something goes wrong with one of my sites which I like because sometimes things do go down at times but not always knowing what went wrong makes me uneasy (even though they have excellent support).
If there were more options available for alerts then this would be perfect - currently only basic notifications are allowed through email/text message. Also could use better customer care since their website isn't super user friendly and requires advanced knowledge to navigate around properly. But once figured out its great otherwise! We're able to see all our websites' uptime stats along with other important information regarding performance etc.