My latest investement is the Sigma 35mm f1.4 A.
I've needed a 35mm prime lens for quite some time, to fill the gap between my 50mm and my 28mm. The available lenses for the Nikon F mount are the old Nikkor 35/f2, the brand new Nikkor 35/f1.8 FX, the proffesional grade Nikkor 35/f1.4, and finally the Sigma 35/f1.4. In addition to these, there are obviously a number of manual focus lenses such as vintage Nikkor Ai(-s) lenses, Samyang 35/f1.4, Voigtländer 40/f2, and the mouthwatering Zeiss 35/f1.4 and Zeiss 35/f2. I really like working with manual focus lenses, but for doing paid work, autofocus is a must for me.
Before purchasing, I read way too many tests and comparison. It all boils down to the following
Nikkor 35/f2 - (€ 300). The cheap option. Also the worst of the lot. Dated technology and not quite sharp enough for current generation digital sensors.
Nikkor 35/f1.8 FX - (€ 550). Reasonable lens for a reasonable price. Even so, € 550 is not exactly pocket change, and I expected much more from Nikon when they announced this lens a few months ago. It's extremely plastic and lightweight, and the optical quality is just barely good enough. Not a big enough improvement on the Nikkor 35/f2 it replaces to motivate the higher price.
Nikkor 35/f1.4 - (€ 1600). Excellent ergonomics, and built like a weather sealed tank. Also great optical quality, but it is unreasonably expensive.
Sigma 35/f1.4 - (€ 800). According to all tests I've come across, this lens is superior to all else in most respects. Meanwhile, it is half the price of the pro-grade nikkor,.. The one major drawback is the less solid build and lack of weather sealing. I can live with that!
In the end, it was quite a simple choice, as the Sigma blows away the competition. Over the last week or so, I've used the lense extensively, and my early impression is that it is every bit as good as I expected. I'm extremely happy with it, so far.