I have been looking into OAS for several weeks now and unless any red flags pop up we will be purchasing a number of 'Flex Tags' from them shortly for a few upcoming projects.
As we are familiar with C#/WPF in Visual Studio and data from an SQL Express database, everything OAS does just makes sense. The tools available that drop into Visual Studio seem to work with very little actual programming needed and give pretty good visuals to work with an already widely accepted WPF format. Web programming and mobile programming through Xamarin looks to be fairly straight forward as well. Within a few minutes of testing, I had dropped objects such as alarming, trending, buttons, radial graphs, and tonnes of other things into a basic WPF window and connected with my PLC using their tag database/driver configuration. I like the fine control details you can do very simply for alarming, user security, database logging etc. Besides the price, I have yet to run into anything I haven't been impressed with.