Well, one of my room-mates was snoring and it was pretty disturbing, but
aside the lack of experience of some reception staff (Alina - that
wasn't aware of their own discounts and maybe Lisa a bit),
everything was 10/10, I'd say.
I'd give an overall 9 to the Hostel, which for the 16 EURO/night I paid (+ 7 for breakfast) was pretty good for my first hostel experience - I could only find similar prices at Hotel Continental during the same period (but having breakfast included and sleeping single in a room - aside having a shared bathroom). I will check Hotel Continental next time only to make a fair comparison.
The location was great: it's 400 m away from the Hauptbahnhof, and
you could just walk to the city center; Novotel Hotel is across the
boulevard and Le Meridien Grand Hotel is a stone's throw away!
As stores, there's an Aldi and a Muller inside the Hauptbahnhof (Central Train Station) and another Aldi on the street going to the city center. Although they might not have the full range of merchandise one might expect finding in a greater Aldi (for example, I didn't find 12-packs of 17 grams Ritter chocolates at the HBH Aldi, but at an Aldi from the outskirts of the city), but you can find almost anything needed for your stay - try the lunchbox-salads (a plastic see-through box containing salad, some-sort-of-meat, cheese, corn, salad dressing and a bit of other vegetables), they're simply great (and pretty cheap at 1,59 for 280 grams and 2,49 for 350 grams)!
The rooms were pretty clean and during one of the mornings, the cleaning staff I met on the corridors actually asked me if they can come inside to clean the room (but I declined).
Another good thing is that I checked-in very, very late: I had reservation from the 26th to the 29th of August and I actually checked-in at 01:00 AM on the 27th of August, so no need to worry.
Although it is written that Nurnberg A&O Hostel charges an additional fee for towels and linens as well as for Wi-Fi (which actually made me pay 25 EURO on roaming so I can have data with me instead of using the - at that time - 'paid' Wi-Fi), both the linens (and bath towel) and Wi-Fi are free of charge. Well, you have to register with your email for the free Wi-Fi (and it doesn't work at all times - but I asked for help at the reception and they made it work). This is somehow opposite to the A&O Hostel in Wien, which charges 3.50 EURO for linens (and I actually didn't get a towel with those!) but still keeps the Wi-Fi free of charge.