[gtsteve]

I was extremely disappointed in the development experience, but the core technology is extremely helpful, depending on your use-case.

If your app is just a mobile front-end for a REST API then I wouldn't bother with it: develop two versions of the app with different UI idioms.

If your app does something considerably more complex, Xamarin might also be a good idea. Keeping two drastically different codebases in sync can be a very big task, but I suggest proactively looking at issues people have experienced with it, as well as other differences such as memory management which works very differently to what you're used to as a .NET developer.

However I think a number of responses have strayed from the question, which is "is it worth learning Xamarin". It appears Microsoft bought the technology because it was useful, not to kill it. I don't think the technology will be retired any time soon and can only get better. So long as Microsoft gives this the TLC it needs, it will be a formidable part of any developer's toolkit.. so long as it can get over the really bad reputation it has.

I for one will explore every possible alternative before considering Xamarin again.