I picked up a new Z30 this week because my 9900 was almost kaput and wanted a reliable case for my device.
Since my experience with Otterbox for the 9900 was so amazing (they've replaced parts twice for me), I decided to pick up a defender series for the Z30. I had read a number or reviews online that said the use of an Otterbox on the new blackberries was more problematic because of the initial swiping motions, but found that once I got use to having the Otterbox on my Z30 it was pretty easy to adapt.
As for the quality, what can I say? It's an Otterbox... it's bigger than any other case, but the design of the case takes the bigger screened device and makes it managable enough to wear on your belt every day. The belt clip is awesome as it's much easier to slide the device in and out than my old 9900 case and despite the size of the device is not very clunky.
Also, as the Otterbox cases have a built in magnet that puts our device in to sleep mode (does anyone other than blackberry have this feature), using the case saves on battery life as well.
I'd definitely recommend that any one considering purchasing a Z30, get an Otterbox to go with it... and if you're considering buying one of those other sissy smartphones, you'll for sure need an Otterbox.
I'm not sure if the Verizon version of the Z30 is any different than the version I got for my Z30 on the Rogers network... if they are the same size then there will be no problem using the Defender Series Otterbox.