The trick for me is not to do the upgrade but clean install. I backup my data and all my program preferences into two identical, physically separate sets. Then wipe everything out, install the new OS, then reinstall the applications and finally restore the preferences and data.
It's more involved but I end up with a clean, fast system. I usually do this once a year, new OS or not, just for the sake of tuning up. It is also a good opportunity to create a complete backup.