I had both the double and single nippers and loved them both. I had them from about 11 years ago and got rid of the last one about 3 years ago. Mine were both second had so the older version, I think the new one is a but more jazzy.
So light to push even the double fully loaded with 2 X 4 yr olds. With both single and double, you can sit (unofficially) a tired legged small child on the front footplate in emergencies. Once we managed 5 kids aged 1-6 in the double. 2 in each seat and 1 on the footplate!
Seats are big enough for tall children. Loads of storage both underneath and in the hood side pockets. Did I mention easy to push?
Tackles all terrains well. On soft sand, tip it up on to its back wheels and pull it backwards rather than push it. Also hose down the metal bits in the chassis if it goes in the sea or they will rust. In woods with lots of tree roots, lift the handle bar like a wheelbarrow and push it just on its front wheel.
Easy to was the seat pads. For a newborn, the Phil and Ted's cocoon fits perfectly. Though they may do their own version now, and I think you can even get a carrycot for them now, they didn't do them 10 years ago. Very light to push even one handed
The only doorway I couldn't get the double through ever was in a grade 2 listed building, it fits through all standard doorways
For all the reasons above and what everyone else says, I would highly recommend.