This turned out to be one of the things you should not do on a Friday afternoon. The solution has several projects: a client on a mobile device, hence CF. A server for web services. And a test project that calls the web services directly for easier debugging, with desktop winforms, i.e., without CF, and with int.TryParse() ... :-) We are also working on upgrading to more modern mobile devices which will hopefully avoid CF.
The bottom line is that VS is not that bad, but not very easy either. Most errors are valid pointers to real problems. On the other hand regrettable that CF is so limited, while today's mobile devices are not that petite anymore.