Very. I have 200+ digital signs running on customer sites 24x7 playing videos, images, live feeds and showing web pages without trouble for over three years now.
All they were used for was displaying a webpage that showed the schedule for a given room in the building so the Cisco boxes were always overkill (and the browser built into it was terrible to boot).
So I put together a test setup on a RasPi that just boots LXDE in kiosk mode, opens Chromium with no...er...chrome on the windows and with no mouse cursor, etc, loads the page for that room, and the page itself handles refreshes. Set a cron job to reboot every morning at 4am in case there was any scheduled maintenance done on the server delivering the webpage overnight. Can SSH in to change things and also set up a node.js script I found that allows me to open a URL in my browser and trigger a reboot or shutdown.
All of this was new to me but in the end, I replaced twenty $1500 boxes with twenty $55 kits and it was an excuse to learn/brush up on some things. The best part is that they look even better now because the Cisco boxes could only go up to 1366x768 and now the displays are running at native resolution. The down side is that this isn't a private company (state university) so I don't get any sort of bonus for saving them almost $30k :(
If you expect this in the private world, you are going to have a very bad time :)
When we first looked at the market, we realized that no-one really knew how it worked because it's still very young. So we decided to compete on price and reliability. Instead of lock-in contracts and up-front hardware purchases, we charge a small month-to-month rental and the hardware remains ours.