Over time I've noticed that as the number of GPO settings applied to my Citrix servers grow, so does the user logon times. I'm using XenApp to provide shared hosted desktops, and the logon times have grown to around a minute.
The solution is to use Mandatory profiles ( and redirected folders ) as long as you don't need for users to be able to save changes. That fits the bill for shared hosted desktops on a server. Instead of having a large number of user GPO settings applied at logon, we're going to customize the profile and save it to a network share, then set a GPO to use this profile for all users. Now you have a profile with all settings applied and you can eliminate many of those GPO's you were previously waiting on to apply. You can use Mandatory profiles along with redirected folders so that users can still get their own desktop and documents folders as well.
Instead of creating yet another tutorial, I'm going to point you to Rob Beekman's excellent blog post on how to create a Mandatory profile.