I love the extended features of this product. You can easily manage profiles and create desktops in minutes. You can also use your desktops on mobile devices pretty much anywhere. One feature that we use extensively is the WAN optimization. Our data backups are offsite, so moving data and virtual machines could kill our bandwidth, but this feature prevents that. XenDesktop 5 is lightyears ahead of XenDesktop 4. It is much easier to use, and the management interface is intuitive.
Room for Improvement:
Sometimes creating good Active Directory policies can be confusing. Also, there is a lot of work in optimizing desktops so that they don't unnecessarily reduce server performance.
High initial cost, but over time it allows a much longer desktop refresh cycle. Our organization is using fat terminals instead of buying thin clients. Once those machines break, we can begin replacing with thin clients.