Thank you for your interest in our UI for Xamarin suite.
When building our controls we make sure we make them customizable and with high performance. With the upcoming styling capabilities it will be possible to apply styles to our Xamarin Forms controls. Once Xamarin Forms 1.3 goes official we will issue an update that supports it.
Let me know if you have additional questions or feedback.
Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.