Silent switch not a huge deal - I only turn that maybe once a day and protection trumps it, The defender covers every port (minus the bottom speakers and mic)
The case prevents easy access to the corners, mostly an issue with the bottom corners with the keyboard.
Must use the anti-glare film, the brand sold at Apple stores but it must be anti-glare.
I thought about taking the built-in screen protector off and just adding some foam around the screen to keep dust out but that would only be needed if you are dust anal-retentive as me.
The impact series is just a silicon skin, nothing too special, but I have never used one.
I would just wait for the commuter series.