I have SQL Server 2008 running on my development machine that I wish to upgrade to the 2012 release.
In your experience, is it better to use the upgrade wizard or to remove the SQL Server 2008 and do a clean install?
Yes certainly use the wizard. It will offer you a tidy upgrade, and can allow for side by side installation with server2008 - if that is something you want. I would suggest sticking to the wizard.