When trying to install the SGP case, I found that the side pieces wouldn't install with the Invisible Shield in place. As I slid the pieces onto the phone, they pushed against the edge of the Invisible Shield. This caused the Invisible Shield to peel up around the edges. I wasn't thrilled with the idea of trashing the Invisible Shield, so I had to find another solution... that being a different iPhone.
I borrowed a friend's iPhone 4 and was able to successfully install the SGP case without much issue. Her phone doesn't have an Invisible Shield, but as you can see in the photos above, the case still causes a problem with the screen protector, causing it to bubble up around the edges. Again, not so good.
Aside from the screen protector issues, everything else looked alright. The sections where the two side pieces join together isn't entirely flush, but it's not overly obvious either. The holes for the various buttons and functions of the phone are all open and usable.
Unfortunately I misplaced the tiny bag with the LED flash diffuser so I was not able to test this feature of the kit.
Let's move ahead and wrap things up with a conclusion.