I used to use the screen lock (pattern)... But it was getting worrisome when someone asked to see my phone and I would have to hand them an unlocked device and give them full access to all my SMS, pics, etc...
So I use app protector pro and keep the screen lock off, and lock my SMS, gallery, email, and other sensitive apps... So if someone picks up the phone I dont have to worry much about where they are wandering.
Written and published from my Incredible II. No need for applause.