Not to speak for Dave Jackson or anything, but I think there's been some confusion in terminology. He spoke of an intermeshing rotor, which is usually understood to be a synchropter design such as the H-43 Kaman Huskie. Although a Ch-47's rotors do intermesh, they are usually referred to as a Tandem rotor and not an intermeshing rotor. And yes there have been many spectacular crashes in the CH-46 (bv107), CH-47 (bv234) family.
Like Dave, I believe the intermeshing design was a great idea because of it's overall efficiency. It has two advancing blades and the weight of only one gearbox, without the power loss of a separate antitorque system.
1) Vs. Tail rotor:
A tail rotor equipped helicopter uses 15% of total power in a hover to counteract torque, which is power unavailable for lift. Plus the obvious advantage of not having a tail rotor to lose.
2) Vs. Tandem:
A tandem rotor helicopter requires a second gearbox and synch shaft which adds several thousand pounds to the Ch-47. Plus the aforementioned problem of desynch.
3) Vs. Coaxial:
The lower rotor has a higher induced velocity and therefore higher induced drag and lower lift. Coaxial helicopters generally have much higher downwash velocities, making them difficult to use in all situations.
4) Vs. Notar:
The Notar spends just as much power on antitorque as a tail rotor aircraft, maybe more. It has the added disadvantage of not gaining any of that back in forward flight the way a tail rotor unloads at cruise speed.
I agree with the bit about rotor danger when approaching from the side. That is a serious drawback. There are also cyclic and pedal combinations that can cause unusual effects, although training and time can overcome that.
It may not be the best aircraft design for the jobs that we do, but from a pure engineering standpoint, it is the most efficient.