The change to the new Vista RDP client can be a drastic one. A lot of things have changed. Several changes break existing functionality that many people relied on.
Windows key sticking:
If you use the windows key + L to lock your machine while working in a remote session, the windows key becomes stuck. When you return to your session, pressing any key that has a combination with the windows key will activate. E for explorer, L for lock, ect... The solution is to use ctrl +alt +del, or move focus away from the RDP session before locking the computer.
Default domain is wrong:
At some point all of our mstsc client forgot what domain they were connected to. Even though my users logged into the local machine with the domain account and tried to remote into a domain terminal server. They tried to authenticate with the machine name as the domain. The solution is to add the domain to the username when typing it in.
Passwords don't save to the rdp file anymore:
You cannot distribute a RDP file with a password. So the user must know the password to use the rdp shortcut.
Login prompt changed:
Not only is it client side, it also has a different look. You can revert it back by adding a special line into the .RDP file: enablecredsspsupport:i:0
Can only save one username/password per server:
This prevents you from creating 2 shortcuts with 2 different usernames to the same server. I read that you can add a second rdp listening port and point one of those to the new port number to work around this one.
At face value, these look like minor issues.
But the amount of support calls and issues this created in our environment tied us up for a long time. All of them user related. Technology is great when its transparent to the users (and does not generate calls to support staff).
We have a good number of users that cant figure out the difference between username passwords and email passwords. (I cant tell you the number of times we have had someone reboot to fix a problem only to have them call back to tell us they cant get the password to work anymore. ) The change that no longer defaults the domain, the change that sticks the windows key, and the different look of the login screen were all drastic changes to them.
We also have a special application that we deploy using RDP. We create a unique account for each computer that connects to it. We would save the password to the RDP so every user uses the same RDP on that machine. Now we have to have every possible user login, then give us the keyboard to enter the password. Not only is that a huge support drain, its an annoyance to our users. (especially to our remote sites that we visit once every other week).
At one point we added a second app to the servers and tried to create a second shortcut for that. Because the hostname was the same, it was only keeping the login details of one username. (we used a different username to access a different published app.)
The sticking window key compounds the problems. Our users don't know the password to that special application RDP connection. So when they get the windows key stuck and press the L key, the remote session gets locked. We get the call and have to remote into that session and enter the password for them.
Our primary solution that works wonders was to upgrade the Vista 6.0 version to the XP 5.2 version. That upgrade fixed all of those problems.
A second solution that I am about done with is to write my own client wrapper for the RDP 6.0 control. We have other issues that I can't solve any other way, and it solves these issues too. I will write up more details on that solution later.