I'm on my third bottle of SDV, two retails and one tester. That said. It's is madly overrated, overpriced and overhyped. For material factors it's the worst of the high-end Guerlains. Compared to the Derby/ALD type bottle or the newer exclusives with the old-fashioned puff style atomizer it seems really unimpressive. Shipping can be a nightmare too because all the packaging and boxing weighs a ton unless you get an unboxed tester. That said the testers have a superior atomizer in my opinion.
As for the juice well it's all subjective. However I really cannot see how it is worth close to $300 unless you're an absolute Guerlain vanilla fanatic. Even then I'd recommend Cologne du 68, unless the sillage is that important. Better vanillas exist. There is no doubt about that. Even Guerlain themselves have better vanillas. The boozy quality and sweetness makes me think of cheap, plastic-bottled imitation vanilla essence to be frank. That's a scent I love which carries a lot of good memories for me so I do enjoy it, but for others this may not be the case. Especially if what you're seeking is a natural, classy vanilla which screams high-end.
I would strongly recommend getting a decant or sample first. Especially if you've experienced niche-quality vanilla scents because it may well leave you flat.
As for whether or not it's unisex I'd say from a marketing standpoint Guerlain are on the money aiming it at women, but that doesn't mean it cannot be worn and enjoyed by men, nor does it mean men will get funny looks if they wear it.