Please get your information right before you post. SL doesn't use have an "archive and install" option, that was available in Leopard. The default installation for SL, when run on a disk with a Leopard system on it, is virtually the same as an archive and install installation, but it does not make a "previous systems" folder. It simple overwrites the old system with the new system and keeps your files and information, network etc.
I have personally found this to be problematic, and had to do a clean install (erase and install) followed by a manual reinstall of data and apps from a backup. The Intel architecture had problems with something transfered over from my G5 Leopard system by the Migration app too. Some people say it worked for them though (from 1 Intel machine to another), so you can try that. Just make sure you have any critical data backed up.