Guys, To get the XFX HD 5770 to work in either 10.6.8 or 10.7 use this driver patch:
http://www.mediafire.com/?gbl7co6eovgi81e
To get Lion to install, use the following parameters: GraphicsEnabler=No -x
at install and at first boot.
Once you have logged on, run the ATI Driver Package (credit to whomever put it together - I found it by accident using Google.) Once you install this package, you will no longer need to use the parameters above.
One my Gigabyte motherboard, all I had to do was install the audio driver afterwards. Everything seems to be working ok.
-Joe