I really liked my stay at Tasman Bay Backpackers. I had a car and didn't want to deal w/parking in Nelson's CBD (especially over holidays) so that lead me to select this place. And I'm glad I did. There is a small parking lot but also a ton of residential street parking. You're 15 minute walk to the CBD, walkable distance too to a few grocery stores (although car is easier if you're picking up multiple items).
There is laundry on-site but dryers are small so use the lines outside, kitchen gets jammed but is well stocked and there are a ton of fridges for cold stuff. Wifi is also great and works well in the rooms.
I was in a 4-bed and had plenty of room when we were full. Each person had their own part of the room for storage and it was pretty cool with windows open. But, there is no insulation in any room (as is common in NZ) so you can hear EVERYTHING. It can get really loud in the kitchen and common areas below the rooms and in the hallways.
Showers and bathrooms are good and clean. Can be busy in the AM but otherwise fine. Nice seating areas outside in front and behind the hostels.
The nightly "pudding" at 8pm is a cake with ice cream and pudding topping. And you should really go at 8pm because they can run out. It's not the most incredible cake I've had but I love that they do it and am sad I will have less of it in my nightly routine.
No real complaints overall. Would absolutely stay again and recommend it.