After 3 Golfs and 2 Octavias, I deserted VW Group in May 2014 for a new Acenta Premium 1.5 Diesel. The Octy is a great car but the spec to price ratio has become a lot meaner of late. Overall, I’m reasonably pleased with the QQ though ownership has not been entirely trouble free. Here is my experience:

Positives

My 2010 petrol Octy was not particularly economical by today’s standards, cost £125 per year in road tax and drank oil as if it was going out of fashion (where did it all go?). It is therefore welcome to be using so little fuel, paying no tax and seeing an oil level that has barely budged in the first 6k miles.
A trip through France in its first month demonstrated how fabulous this car is on a long run on good roads. The cabin is comfortable and well arranged. Nissan made much of the seat design. They are very comfortable though no more so than the Octy seats which seemed to me to offer more side support. There are many bells and whistles and I love the reversing camera - a facility I’ve never had before. Other things I like are the auto dipping headlights and speed sign reader. The satnav works pretty well though I’m expecting a large bill for software updates (I’ve read about this elsewhere)

Not So Positives

As has been well noted, the rear view is very poor but the camera and sensors more than compensate for this and make reversing in and out of tight spots easy. I was prepared for a little less performance than the petrol Octy. In the main, this isn’t a problem for me though it required a big change in driving style involving much more gear changing (due also to gear ratio arrangement). There are some irritating features like the rear seatbelt warning that has to be cancelled before you can see the parking display (or any other display). Another is the inability to fold the mirrors with the key from outside the car. There is also no warm air feed to the rear passengers.
Road noise can be disappointingly intrusive on some surfaces though is generally ok.
Finally, since taking ownership of the car, there have been many (mostly very minor) niggles which leave the distinct impression of a lack of quality control, attention to detail and/or the use of cheap materials. These have included:
1. When I opened the glove compartment for the first time I found was a small plastic rectangle. This was the cover to the fuse box at the rear. I replaced it and closed the glove box. It came out again. It turned out that some of the wiring behind was proud and folding it back gently resolved the problem.
2. The first time I folded down the rear seats one of the catches fell to pieces and had to be replaced. (2 trips to the dealer)
3. In wet weather or after a wash, the front parking sensors fired off randomly due to the ingress of water. In initial trip to the dealer failed to sort this out. There was then a recall for a software update which was supposed to resolve this - it didn’t. Finally I found a contributor on the QQ owners website who had experienced the same problem. His dealer had obtained modified sensors from Amsterdam with extra seals. I printed this and took it to the dealership. Sensors eventually replaced and problem solved. (4 trips to the dealer). There are now many owners raising this issue.
4. The boot light kept falling out due to a cheap fitting in the soft boot lining. I eventually managed to get it seated properly after several attempts.
5. I noticed an external door trim was not flush with the door in one place. The clip was not properly seated and I was able to push it back in and get it to stay put.
6. The seal at the bottom of a rear door came unclipped at one end. Again a poor clip arrangement which I pushed back in.
7. On a couple of occasions the car has failed to recognise the key, so I couldn’t start it. On both occasions I got out, locked the car and started again which solved the problem.
8. Recently loud alarming vibration was coming from the engine compartment at low revs. I traced this to the two-part air inlet which was rattling against the air filter box on the bulkhead. Again a poor clip arrangement was to blame. Some attempt at the dealership to resolve this with foam tape was not wholly successful and a new part is on order. (1 trip to the dealer so far…) At the same time there was another recall for software updating.

A relative of my wife was a test engineer for another manufacturer. He used to drive cars around for several weeks to road test them before launch and identify minor niggles / rattles and so on. I can’t help feeling that Nissan could do a bit more of this. It's not exactly a bargain basement car so these niggles are disappointing.
Having said all this, the dealer (JFE Exeter) has been as helpful as one could wish, but I didn’t expect to be seeing so much of them so soon.