I just planted 4 of these about 2 weeks ago. I'd say they are growing extremely fast and the stems are the thickest I've seen on a seedling, giving me a lot of hope. I tried the NL auto from G13 and it basically failed hardcore. I had one that popped it's 2nd set of leaves before it even had the seed completely burst off(the nirvana, not the g13)! I know that the old nirvana AF's were problematic and they were taken off the market for a while, but I'm going to grow it like an autoflower. I'll sub your thread if you want and let you know if it starts flowering on it's own or if I have to swap the cycle ect. I'm not too far ahead of you so hopefully I'll be able to help. I'm growing it in soil (I always grow my AF's in soil) and it germed and is growing very well. I know a lot of people buy northern lights from Nirvana and just start them on 12/12 which would be basically the same effect, but an AF would be faster. So far I'm very happy and it's looking like by far the strongest early showing from an AF I've ever had. Deep greens. As far as autos, value-wise they are really good for an auto. I'd say go for it man. They just put them back up so I'm assuming they stablized the pheno's. Good luck and hope I didn't steer you wrong!
BTW I'm running them on 19/5, I've never really liked 24 straight I like them to have a chance to cool off.