I wanted to know if the summilux has the "double line "effect that the nokton seems to have under some particular light situations.
Debusti, are you perhaps thinking of the 35mm f1.2 Nokton's little sibling, the 35mm f1.4 nokton? The "double line effect" frequently is mentioned about the f1.4 nokton, I can't remember it in conjunction with the f1.2 nokton..
Irrespective, I've got the f1.2 nokton and it's a brilliant lens, with gorgeous bokeh. I'm still a month from buying a film scanner, or I'd wade in with some examples of my own. If there's a reason to NOT get the f1.2 nokton it surely couldn't be the bokeh! If you're a bokeh nut, the extra 1/2 stop of the f1.2 nokton actually gives you more bokeh range (and light-gathering abilities) to play with than any other 35mm lens on the market.
The build quality and handling of the f1.2 nokton are great, optically it's terrific, and the price is very very reasonable (astounding price to performance ratio, I think). There's no lens I'd rather use at any price for low available light shooting (including the noctilux - although if I had that much spare cash I'd pick one up anyway). To my mind, the only controversial thing about the f1.2 nokton is it's large (by RF not SLR standards) size/weight. For me and for many others it's totally worth it. For some people it's not.
That said, the Summilux would be a great lens too. I haven't used one, but I bet it's great. It does have some notable critics who find the bokeh and rendition overly "harsh", but I really don't think you could go wrong with either of these two lenses - cost notwithstanding!
