One of the things that I am a firm believer in is the ability to bond porcelain to teeth. Lets face it, it works. It works well and it's proven.
With so many bonding agents out there and companies working on ways to make the process easier and easier, what we are finding is that we have the ability to really have great bond strengths with our materials. So as I've moved more toward self-etching bonding agents such as the 3M Scotchbond Ultimate or the Kerr XTR bonding agents -- I still like to selectively etch the enamel. If there is a lot of enamel remaining, I feel that you still get the best bond strengths to enamel by etching it. Keep the etch on the enamel and not on the dentin. Even if I use one of my favorite cements such as Multilink, I still like to etch the enamel.
This may change in the future but for now- enamel etching is where its at.