No doubt about it, Back to Black is the masterpiece of the Kilian line - at least as of the year ending in 2009.
If you like the opening of Back to Black, the good news is that it only gets better. Personally, I'm a little iffy on the opening but it passes soon enough. The opening consists of raspberry and honeyed cocoa which is a bit too sweet for my taste but the sweetness mellows fairly quickly and leaves behind this golden smokey tobacco with undertones of tonka bean that is just to die for. It leans ever so slightly feminine but I wear it often and receive compliments, so I'd say this one is fairly unisex.
If you don't like tobacco notes or you're in the market for a totally average workplace scent, this is the last fragrance you should be looking at. This is a very special scent and the only Kilian that I think justifies its price.
Personally, as much as I like it on myself, I think it smells ten times better on a woman. It is by far the sexiest fragrance I've smelled on a woman - not in an overly sugary/annoying way but a very sultry and determined way. Probably my favorite release of 2009.