The Curtain is pretty good but I really want something else...

Working backwards up your post:

Why does the remote screen need to on at all when I log in?

The screen doesn't have to be physically turned on. But ARD takes control of the current user session, so if you're connected and someone turns the screen on, they'll see your work unless you use Curtain Mode.

In addition I need it to Lock the remote screen when I lost my connection.

ARD does not have such a feature. In fact it's not a feature most admins would want, since such a feature would lock a user out of his/her system if the admin's connection would happen to break. I don't know of any remote control system that offers that capability.

My most frequent usage of Remote Desktop is to use the remote computer and not to control, configure or adjust it.

I don't know what you're doing, then, by "using" the computer but not "controlling" it. If you can clarify, perhaps someone here can suggest a way to accomplish what you want.

Regards.

If you want the screen lock to persist after your connection is closed, might I suggest setting a password on your screen saver? That usually works with me. There are even a few applications what will provide a keyboard shortcut to automatically run the screen saver and lock the screen.

That can't be done with ARD, which only allows you take control of an existing user session. You can't create a "virtual" session that's not reflected on the screen, at least by any method I've ever come across. The only way to keep people from seeing your work is the Curtain mode which, again, works only when you have an active connection to the system and cannot be activated automatically when the connection breaks.

I'm not aware of any Mac workstation software that will give you the functionality you want for applications that use the Mac OS X GUI (rather than X Windows or UNIX command line). Vine Server would allow you to connect to a user session running via Fast User Switching, but that still would require another user to be logged in an active in the foreground, though you could perhaps use a "guest" account with very limited capabilities. I don't know if Vine Server works with anything newer than 10.4.

Aqua Connect purports to provide virtual-session capabilities with Mac OS X Server, but I'm told it's pricey (they don't post pricing on their webs site). They hint at a workstation solution, but have provided no information about what it will offer.

Regards.