I've been using Syncfusion Essential Studio within WPF for a while now and the quality of the controls really are superb. We've incorporated the Ribbon control into our application quite successfully now and the flexibility that these controls offer is pretty amazing. There are several suites out there at the moment offering similar functionality, but having evaluated them all Essential Studio was a clear winner. The samples are continually being updated and redeveloped to take into account changes to the toolkit which is nice as it really makes you feel that they are continually moving the product forward with new developments. I should also mention that the support is second -to-none. On several occasions I've had the need to contact them, for either bug fixes, feature requests or sometimes just for some assistance. Every time I've had a quick response and quality reply. For bug fixes they have supplied patches very quickly indeed. If the first response doesn't immediately meet your requirements then they seem happy to continually work through your problem until you are satisfied with the result.