no, you cannot give a Carnifex (or anything else) double cannons, check the notes.
I really want to like this codex, but I've been feeling the same thing that was mentioned on page 1 of this thread, where I'm feeling ripped off to have paid ~$50 for this book. Yes, some of the points values got tweaked, and I can't honestly say I'm sad to see Ymgarls gone. But between the 50% jump in points cost on Warrior Primes, and the loss of Mysetic spores, a whole lot of tactical options just went up in smoke.
Griping aside, I feel a moral obligation to add something constructive to this thread.
+ Biovores which miss... don't.
Spore mines placed by a Biovore miss are not arriving from reserve, so, as far as tonight's opponent and I can tell, get to charge immediately after having missed their target.
+ Psychic powers aren't bad.
Yeah, gone are the days of the Tervigon choosing the best of three different powers, and gone are the days of Blink-a-thropes gating into enemy backfields to slag tanks. but at least everything on our psychic power list now seems useful, and at least Zoans are guaruntied to get thier signature power.
* I view the Haurospex as the ultimate terror weapon. If it reaches the enemy line and starts charging things, it is going to be an extrodinarily difficult model for your opponent to get rid of. Splurge on the regen, and that jumps to nigh-impossible. (though I'd advise forgetting about the claws altogether) Take two to make sure this happens, or just one to give the rest of your force a pass from enemy fire for a while.
At first glance, they seem nerfed in that they only give shroud to the MODELS in 6" of them, but the shroud rule itself confers this benefit to every other model in the unit. Either way, you need more than one if you want them to stay on the field. It's nigh impossible to convince a determined opponent that they don't have a shot because the line of sight through the ruins, over the termagants, and between the Tyrant's legs just doesn't exist. In fact, I think I can remember one time convincing anyone they didn't have any shot they wanted since 6th ed came out.
The screaming ball of hate that is three carnies charging across the table got a lot more affordable, and with the (much nicer) Living battering ram rule, getting in front of them is unlikely to be covered by one's life insurance.