Hey Stefan, you’re also free to use services such as Pingdom to monitor your pages. I should also add that you can check out our uptime on http://status.unbounce.com as well, though that only shows the last 30 days right now. I just checked our one year number as reported by Pingdom, and we’re at 99.9958% uptime on our servers (22 minutes of downtime in the last year, or less than two minutes per month on average.
As a matter of course, we don’t take our servers down for maintenance or upgrades, so the only downtime we ever experience is if there are operational errors or issues with hosting (which is reasonably rare because your Unbounce pages are hosted in four Amazon data centers around the globe).
Anyway, welcome to Unbounce, hope your transition goes smoothly!