I have an app using Xamarin.Forms targeting IOS, Android and WP 8.
I need push notification feature in my app.
I have seen the pushsharp
demos
I have been suggested to use the following plugin by xamarin support and forms.
This plugin works well
https://github.com/rdelrosario/xamarin-plugins/tree/master/PushNotification
Will update the answer once I get it to work.
UPDATE :
I got push notifications working for both iOS and Android.
I used Google Cloud Messaging Client, an excellent component for Android, and didn't have to write much of the code as mentioned in this answer.
My iOS implementation was similar to this, not much code required.
And for Pushing the notifications from the Server I used nuget package of PushSharp.
I didn't implement in WP, as that was not required in my project.
This Xamarin Help on Push Notifications is worth reading if you are going to implement Push Notifications.
Update (June 2018) - Use the following plugin for FCM on iOS and Android, ti supports Xamarin.Forms - FirebasePushNotificationPlugin