I have spent a lot of time with Oracle support in the past year helping them to train them on OVD and OAM (the latter mostly focused around OVD-OAM integration). And really they are a great organization.
Chris Warticki who works in Oracle support maintains a blog and has a post containing a good customer testimonial on everything support does.
My additional advice on getting the most from support:
1 - Read this post from Chris on benefits of support best practices training
2 - Take the free support training class http://www.oracle.com/support/seminars.html