It's hard to post likes/dislikes of Nelson in contrast to elsewhere in NZ, since it's the only place we've spent a significant amount of time. Also, it's hard to truly compare it to our home town, without knowing how much of the difference is Nelson in particular and how much is NZ in general.
One of the only disappointments is probably NZ-wide, I'm guessing. I thought there would be more organic produce. Admittedly, we're coming from Central Coast California, where you can hardly swing a stick without hitting an organic farmer. :-P However, even the store called "Organic Foods Nelson" has very limited produce, they are better for bulk foods and dry goods (and they're pretty small.) We went to the Saturday market, which did have some local produce, but some of the stalls were clearly using the same sources as the grocery stores - including pineapples and shrink-wrapped cucumbers. What's up with that?
The ocean doesn't really compare to Santa Cruz, it's walled in by a boulder barrier and still as a pond. Tahunanui and Rabbit Island seem to be where people go to play in the sand, and those are certainly nice and close, but riding your bike along the ocean has more views of mudflats than waves. We did take a trip out to Abel Tasman, which is absolutely gorgeous, but there is the stress of catching your ferry or being stranded.
These are pretty minor factors, and otherwise I'd say Nelson measures up to expectations. I still feel like there is plenty to explore in terms of dining, events and arts, walks and bike trails, etc., and wouldn't expect to run out of things to do if we lived here. The weather has been mild, and often gorgeous. We did get some rain and grey days of course, keeping the garden green and moist.
I suppose the only thing I would change is not choosing a house location for walkability, unless we were REALLY SURE we were going to walk or bike much. The seven year old couldn't handle the hills without complaining and foot dragging, even though were just 4-5 blocks from downtown.
If I were moving here, I would be sure to check out the school that was in-zone...but that's for anywhere. The school the girls were able to attend didn't have a zone (Auckland Point School), and the academics were pretty remedial - more of a play/socialization environment (which was great for visiting, but otherwise...not). If I could choose a primary school, I'd go with Clifton Terrace, I was impressed with the tour.