To give a view from the other side of the fence...
We've travelled a few times with our oldest (now 3) in Business on BA and AC, and once with both our children (now 3 and 1) in NCW (we've got another NCW trip coming up - I won't scare anyone off by posting dates!). We've also taken them both in WT+ a few times. All of these flights have been long haul - West Coast NA. We've had other flights in Europe in economy.
I don't think I've ever travelled in a premium cabin with the children without an overpowering sense of foreboding. It's really quite grim, and can stop me enjoying the flight. However, the truth is rarely as bad as the anticipation. Generally, the 3 yr old is fine - she watches TV and curls up.
The problems mostly have come more from the younger child, or the older one when she was at that age. At 1-2 they're still at an age when they can sometimes cry for no apparent reason, and certainly can cry from being overtired but not able to get themselves to sleep. Some children need "cues" to get them to sleep - music, lighting, their home bed, etc. It's tough to work around that on a plane. Moreover, air travel is still exciting, if you're a kid! It can be hard to get to sleep when you're excited.
No matter how irritating you might think it is to have a crying baby/toddler in the cabin with you, it's quite a bit worse when it's your child, they're crying next to your head, you can't do anything to placate them (let alone given your fellow pax some peace!), *and* you've paid 110% of the seat price for the privilege.
So, spare a thought for the parent next time you hear a baby/toddler crying in a premium cabin. I get the impression that some of the seasoned travellers here harbour suspicions that parents ***** their charges with sharp objects just for the hell of p*ssing everyone else off - it's just not like that!
Personally, I can't wait until their old enough to travel alone in econ (which they would love as (a) it will still seem like an enormous seat, and (b) it will give them independence from M&D) and we can travel up front. But's that's a way off.