Deanna,
I know of a couple dozen instances of companies running EV Extensions on Citrix.
You will need to be aware of the following:
If Outlook 2000 is installed on the Terminal Server, the user sees the following error when they try to view an archived item:
The form you selected could not be displayed. The form required to view this message cannot be displayed. Contact your administrator.
Can't open this element. Can't display the form. Contact your administrator.
To resolve this issue, install Outlook 2000 SR1 and apply the steps outlined in this article:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;249965
and
Forms with VBScript do not work with Terminal Services in Outlook 2002 and in Outlook 2003
If Outlook XP is installed on the Terminal Server, nothing happens when the user double clicks on an archived item to attempt to view it.
See this article for details of the problem and solution:
http://support.microsoft.com/default.aspx?scid=kb;en-us;302003
What issues are you seeing trying to un-install?