We stayed at Northern Lighs Hotel last October and it was a nice surprise. Hotel is very clean and staff is really nice and helpful. I recommend you to book the transfer from the airport to the hotel directly with them, it's not expensive (40 euros a van for 4 people, I suppose a smaller car will be cheaper) and the driver is very nice.
Hotel is placed at the third floor of an old building, a kind of palace (please, notice that there is no lift in the building). Although the hotel is new and everything is ok, I can't say the same about the entrance and the stairs of the building. When we arrived we were quite scared (it smells really bad and it looks like the last painting of the stairs was before Russian Revolution). But when you arrive at the 3rd floor and pass the door everything looks better. I think that's one of the reasons of the low prices...
You'll get breakfast at your room. It is not the best breakfast in the world, but it is OK.
I would definetely recommed this hotel and would repeat. St Petersburg is a very nice city and the hotel is located really close to St Isaac Cathedral.