I've found the answer to this part, at least.  This behavior was the
result of having a Group Policy setting enabled:

Local Computer Policy > Computer Configuration > Administrative
Templates > Windows Components > Terminal Services > Always prompt
client for password upon connection

(I wish it were buried a few levels deeper.)

With the above setting "Not Configured", I get right to the remote
desktop after filling in the credentials on the "Remote Desktop
Connection" dialog.

I've had that Group Policy setting that way for years (which is why I
had forgotten about it).  Why it behaved differently with the previous
TSC I don't know.

Hello,

try and use the "Do not use authentication" option in the Advanced Tab sheet
of
option. This does not persist however so if you want  to make it permanent
add following line to the default.rdp file (or any other saved .rdp
file):enablecredsspsupport:i:0

That will take care of it.  Cheers

The new client can give roughly the same auth behavior as
the old client, it just works a little different on the front
end.  You do not need the enablecredsspsupport option
that I discussed in a prior post:

http://groups.google.com/group/microsoft.public.windows.terminal_services/browse
_frm/thread/7048672478cf3141/

I recommended that option because the poster specifically
asked for the old behavior and because he is using the
Novell client.

What behavior would you prefer, exactly?

When you run "mstsc [filename].rdp", would you like it to:

1.) Connect and log you in to your XP Pro machine, without
prompting for username/password at all?

2.) Connect to your XP Pro machine, but stop at the Log On
to Windows prompt, with your user name pre-filled and
the password box blank?

3.) Another option?

I am guessing you want option 2 above, please correct me if
I am wrong.  Remove the enablecredsspsupport that you
added before.  

In order to do this, you need to open up the client (manually, not
specifiying .rdp file) and connect to your XP Pro machine using
the same computer name stored in your .rdp file.  When
prompted for your credentials, enter them exactly as you would
if you were entering them on your XP Pro machine, and check
the save password box.

After you have successfully connected, disconnect from
your XP Pro machine.  Open up the client again, make sure
the computer name is still set to your XP Pro machine as used
above, and then click the edit credentials hyperlink.  The
credentials screen should have your username as entered
above, with the password box blank.  Click the OK button
to save your credentials, do *not* enter a password in the box.

Uncheck "Always ask for credentials".  Optionally set all of your
connection preferences and then click the Save As button to
make a fresh .rdp file for this connection.

Click the Connect button.  This time it should connect to your XP
Pro machine, but stop at the Log On to Windows screen with
the user name field pre-filled and the password blank.  You
should have the same behavior if you use the rdp file as well.

Username and password are no longer stored in the .rdp
file.

Please let me know if you have any questions.

-TP