So - verdict? Here is the one minute review:
Pro: The app does what it says. The code completion is there, the suggestions are sound. Creating apps is pretty simple, though you can also create scripts. It isn't doing anything funky - it is just straight up C#. The extra characters given above the keyboard are sufficient. Nothing overly bad is grabbing me outside of my Cons below. I feel like it was a sound purchase, and I'm happy to support the developer!
Con: On the iPhone the screen layout is getting in the way a little. The code completion window was hidden under the keyboard when I tried to do something less trivial than a simple script. Writing the most basic console app failed with a NullReferenceException:
... var r = Console.ReadLine(); Console.WriteLine(r); ...
It seems like the console isn't 2 way? This even works in LinqPad, so I'm not going insane - it's valid code.
Overall, I think it is a neat little tool. Fairly polished, but it needs to be tweaked over the next few months to improve some of the features.