We use Pingdom and it's awesome. The dashboard is really nice and the service is very reliable. My sole complaint is that their starter plan only includes Real User Monitoring for one website. Have to jump up to the $46 / month plan for more RUM sites.
RUM is definitely a big value prop. I like keeping an eye on how quickly our site loads in different countries and on various devices.
For analytics we use Clicky and it's decent. There's a 3rd party Chrome extension which is useful for seeing, at a glance, how many people are on our site.
Another big value prop is integrations with services like Slack.