I'm seeing a really strange issue with calling a WCF SOAP service. We added the service reference to a PCL that is then referenced in iOS and Android (and Windows Phone which doesn't have this issue). I've only verified this on Android so far but I wouldn't be surprised to see it on iOS too. We have a method that returns an object that contains a float value, and this float value is almost always correct, but we started seeing an issue when returning a -100, and after deserialization the result would have a 156 in it instead. After some troubleshooting we have found that any negative whole number in a float value actually gets returned as the expected number plus 256, so -1 comes back as 255, etc. This doesn't happen with decimal values.
I have also reproduced the issue when adding the web reference directly to the Android project. It's kind of difficult to set up a simple repro for this but if you need more let me know.