I have a fair few hundred .nets and they perform well within the engines and as sites in general. I think people tend to bounce to a .net If they cant find the site on the .com, I only do this when hunting for companies outside the UK though, and also when I'm not googling.
Also. If I'm on a .com site which is industry specific e.g. cars - I sometimes browse the .net just out of interest to see whats there too.
As I monitor deleting .com's and net's I picked up one which I plan to brand as a company very shortly " 3Dinter.net " so i'll be able to tell you more once my experiments over.
BG