Yeah I know, its a dilemma, I think I will eventually go for the SB 600, since as, you say, nikon products (more flashes than lenses I suppose) are more reliable and of betetr quality. It would be interesting however to hear from someone who has one of the Sigma flashes, though, I guess its a sign in itself that so few buy them, maybe its not so good.
And yeah Im very excited about the lens, hopefully it will be of good quality, if not I can exchange it I guess. Ive looked around at pictures people (mostly on these forums) have taken with it and I'm impressed.
Anyway, thanks for your feedback, always good to get a second or third opinion on stuff like this, especially since I'm only a couple of months old (photo wise).