Guanfacine is an antihypertensive that is used for ADHD as a 3rd tier med. Shire will be marketing a long acting form for ADHD. As Embmom said there is a great deal of info if you search the medication board topics for the key word tenex (which is a brand name for guanfacine). Here is one of those threads with good info:
http://www.adhdnews.com/forum/forum_posts.asp?TID=24770& KW=tenex