We have been using the cloud for 2-3 years now. We have over 100 PCs spread across 5 different offices. There have been ups and downs during this time but overall things have been mostly up. As far as WinOMS being just down and unavailable, that doesn't happen often or for long. Our biggest issue is when xrays take too long to get to the cloud. We have been good for a while now, I probably just jinxed us by typing that, but there were times when a simple pan we took wouldn't show up in OMS Imaging for hours. They moved us from one server to another many times and now our xrays take about 30 seconds.
A work around we did was to install Imaging & other required software. This then prompted us to choose Cloud or PC access when opening Imaging. If things run slow, then we can choose PC and see xrays immediately. There are a few draw backs using this method but at least we could view xrays in the exam rooms. We also have 2-9300 CBCT machines. If we take a CT, they go to the cloud in real time and are available after several minutes. If you have more questions, I'll be happy to give you honest answers as a cloud user.
Just let me know.