I recently stumbled upon a client where the login time could be classified as not of this world. For me, any login time exceeding 10 seconds is to be considered too long. I'm not talking about boot-up time but the time it takes for the desktop to appear after username and password has been entered. After the usual investigation relating to the network, DNS and Group Policies, the problem was found in the event logs.
Say hello to nearly 4 minutes of Folder Redirection processing. As it turned out, the user had made its entire home folder available offline which caused these dramatic effects to the login time as the number of files exceeded too many to be mentioned here. The solution was simply to not make the files available offline and clear the temporary cache which decreased the login time to a respectable 5 seconds.