I have tried just about everything I can think of to get that panel to do
what I want it to and the closest I have come is this:

First, you need to install compizconfig-settings-manager:

sudo apt-get install compizconfig-settings-manager

Then, open the dash and type ccsm, then click the icon to open the settings
manager. Scroll down until you see the 'Ubuntu Unity Plugin' and click on
it.

On the 'Behavior' tab, set the 'Edge Reveal Timeout' to the highest
setting. This will let you put the mouse pointer on the left side of the
screen for about 3 whole seconds before the panel appears. It will be
temping to change the reveal mode and try to put the panel on another side
of the screen, but it didn't work the last time I tried. The launcher just
disappeared and I couldn't get it back. Where it says 'Hide Launcher'
choose 'autohide'. The default key to show the launcher is the 'Super'
key, the key with the windows logo on most pc's. You can change that to
any key or key combo where it says 'key to show the launcher'. Just a
warning, don't go messing with the desktop cube or any of the other more
adventurous compiz settings unless you really know what you're doing or
want to experiment and don't mind losing your desktop completely. Annotate
is pretty cool though, that one works with unity.

On the 'Experimental' tab, I set the 'Panel Opacity', 'Launcher Opacity',
and 'Launcher Icon Size' to the lowest setting, so even when they are
there, they aren't there as much. I have been able to live with this
configuration quite well, and am looking forward to 12.04. Hopefully they
will work in more configuration options.