Just got my Defender case today - Thumbs Up!
This is a really nice case if you can live with the extra bulk it adds. As much as I tried getting used to carrying my iPhone 4 in my pocket, I just couldn't get used to it (the result of wearing a belt holster for a Blackberry for years), so I wanted a holster case that also provided protection to the phone, and this is probably the only thing out there now that fits the bill. As others have mentioned, the silicon cover is not sticky or tacky; it's pretty "dry" to the touch, and almost slippery. The parts fit together very nicely, and the holster works well if you can live with the bulk. You can put the phone in screen in or out in the holster, which is key because you can protect the screen from bumps. The screen protector has a bit of a rainbow effect you can see when the phone is off, and does add a little friction, but certainly no worse than the Zagg IS protector I had on the phone (which I took off). The front camera is covered by plastic/screen protector (it's actually a separate piece from the main screen protector); the rear camera is not covered but probably is as well protected as you can make it without covering it. Otterbox claims no issues with the flash, and others haven't reported any, so hopefully there won't be.
All in all, very pleased with the case. If I didn't need to be able use a holster, probably would use something smaller like a Candyshell case or just a screen protector and the bumper.