I have just (successfully) upgraded my workstation from SL 6x to SL 7x 
.  Several observations:

I manually configured both the network and the hard drive resources.  
Before the actual installation started, there was a warning that I had 
not set either the root password or a user account.  I tried to address 
these before the actual installation started, after choosing the 
partitions for installation of the SL 7 required 
applications/directories, but the installer froze with a request to send 
an error message to the upstream vendor -- and the sending did not 
work.  Upon rebooting and restarting the install, I found that the 
partitions/disks had been changed, but no packages installed (I had to 
configure the network information, etc., again).  This time I let the 
installer install all of the packages, and then assign the root 
password, user account, etc.

There are a limited number of default configurations.  However, there 
seems to be no way to choose the specific packages to install.  Is the 
assumption that these will be done post-install?

Yasha Karant