We have a couple of websites that are business critical which we need reporting on up time and performance in order to monitor our SLAs.
Although Super Monitoring isn't free, it has saved us a small fortune we could use in a dispute with a vendor regarding uptime of a mission critical website.
Setting it up is straight forward and there's not much to it. As far as we can tell the product is accurate in reporting and monitoring any faults.
It also gives handy information like pings and performance. I've contacted support once and I've been impressed with the professionalism and speed at which they've replied.
The main downside is the price as there is other products available that does a similar task for free or cheaper. I'd happily pay the price knowing I have a reliable product and hassle free setup.
I'd make sure to understand what the product does before buying it.
We need to have accurate reports of uptime/downtime and performance monitoring. Super monitoring does the job very well.