Echo'ing what others have said: PLEASE add a line like the following to the README and to the installation debug page - a little documentation could save many people many hours of installation frustration:
"If you're accustomed to installing WordPress by hand, note that you should NOT attempt to create the wp-config.php file for WPMU in advance of installation. WPMU installation *will fail* if wp-config.php is present."
I'd also suggest that the README should include information on permissions.
Finally, a recommendation for the installer screen, once you do get it up. The field asking for the "shortest possible blog URL" doesn't say what to do if WPMU is installed in a subdirectory. Does that field want just the domain name, as the example shows, or the domain name plus path? If path, should it include trailing slash? Now that I've got basic install done, I'm getting infinite redirect errors and am not sure what's causing it, but suspect it has to do with the presence or lack of a trailing slash on that field.