Yeah, verticals aren't great in thick mud as they just clog up.
However on virtually all other surfaces they grip pretty well. They certainly aren't puncture prone; I've only ever had a few snakebites mostly from DH stuff, but that's because single ply tyres for DH should be avoided like the plague (I didn't have any dual ply at the time though).
They are a very underestimated tyre. Took them to the Dyfi forest down all the Motocross stuff and they stuck pretty well with no problems. They gripped the loose shale on the Dyfi enduro no problem and filled me with confidence.
To all those who knock it for it's mud problems:
The manufacturer who makes a perfect all-condition tyre that rolls well over all surfaces will drive everyone else out of business, and don't exist yet. The Verticals are a great tyre that work pretty well on everything except deep mud (where you probably need a proper mud spike anyway)