After putting 120 days on my Nike ZF1s and getting the beginnings of peroneal tendonitis, I knew it was time to replace my boots. I went with the Kaijus because I knew they were stiffer, and I needed stiffer.
The ZF1s wore in great up until the end (I could basically fold them in half at the end). After the normal 5 or so days of break-in, the Kaijus had the same great comfort. They also seem to be slightly warmer, which was a major issue with the older ZF1s - my feet would freeze in anything lower than 25 F temps. The kaijus were toasty as low as 15 F - though I didn't get a chance to test them any colder.
I only have one concern, and that is that the kaijus seem to have a lot of space in the toe box. My toes just barely touch the end of the toebox, which is a perfect fit. However, they just seem too comfortable. I have about 20 days on them at this point, so we'll have to wait and see. After telling my friends about this, their only reaction was "it sounds like you have the perfect boot".
I have somewhat narrow feet, and I downsize 2 sizes (normally wear a 9.5 or 10 street shoe) and the Nike line is perfect for me (I tried Burton, Celsius and thirtytwos in the past). No heal lift. Traditional laces let me fit my boots just right.
As an interesting aside, I've had people say things such as "Nike isn't a snowboard company, buy Burton", to which I reply "Burton isn't a shoe company, buy Nike". As it turns out, Nike poached THE boot guy from Burton to start their snowboard boot line - so you're not working with crap technology. Honestly, I don't know if I'd ever buy anything Nike otherwise, but these boots are great.
All in all, 20 days in on these Kaijus and they are just the step up in stiffness I wanted coming from 120 days on ZF1s. I highly recommend them. They're supportive without feeling like you're wearing a box on your foot (that's how Celsius boots feel on my feet).