At first I upgraded. Everything was okay, but not great. Little things like Spotlight not indexing properly annoyed me. Also, I wanted to finally and properly get rid of Norton so I saw it as an opportunity to do an erase and install. Everything's great, I'd recommend it to most users who don't mind having to reload in all their music, photos etc. Of course, if it's too hard, then an upgrade seems to generally work pretty well too.