Here are the main
facts from the catalog:
Size: 80x137mm = nice size

21mm longer than the Nikon 105/2.8 and 7mm shorter than the Nikon 180/2.8
Weight: 833g w/o caps and collar but including lens-hood = very "bearable" and only a little heavier than the Nikon 105 or 180
Optics: 16 elements in 12 groups = much too much for a fixed focal

The 105mm micro-Nikkor is a 14/12 design and the (non-micro) 180mm Nikkor is a 8/6 design
Closest focus distance/max.magnification: 38cm / 1:1
Filter-thread: 72mm = standard
No
IS = very bad
AF: HSM, so does work on D40/x/D60-bodies

, manual-focus override by turning the focus ring
Covers
full frame/FX or smaller = normal
Comes with an nice looking
lens-bag
Price: around 580€ new = not exactly cheap
The front-
lens-cap is the new pincer-type like Nikon's

the rear-cap is cr*p like ever
Distance information is relayed to the camera, so the Nikon body can do all the advanced exposure-related stuff with this lens
Aperture ring = no, just like a Nikon G-lens
lens-shade included and revertable for transport
Tripod-collar can be removed without dismounting the lens

, easy to turn camera to portrait-mode
Limiter switch: Yes, with two positions: "full" or 52cm to infinity / 38-52cm.
Sealing: No

unlike the Nikon 105
Versions:
As to lens-mounts: There are versions for Nikon, Canon, Sigma and four-thirds.
Motivation:
Now why should one get the Sigma 150/2.8 besides the micro-Nikkor 105/2.8 VR and the Nikon 180/2.8?
- It's almost 50% longer than the micor-Nikkor, almost as long as the 180mm Nikkor. So a nice length for all those hard to reach subjects
- It's at least as sharp as both of the other lenses
- It can go 1:1, whereas the 180mm Nikkor can only reach down to 1:6.6 which is definitively not enough macro for my liking
- It has the same large f/2.8 aperture
- It has much less Bokeh-CA than the 180mm-Nikkor
- It has a faster focus than the 180mm-Nikkor
So I will surely sell the 180mm-Nikkor if the Sigma holds up on IQ-promises!
Alternatives:
- The
micro-Nikkor AF-S 200/4.0: An excellent lens but longer (19.3cm) and heavier (1.2kg) and not as fast. It's also quite pricey at around 1300€ new
- The
Nikon 180/2.8: A smallish fixed focal with excellent IQ were it not for the surprising degree of Bokeh-CA
- The
micro Nikkor AF-S VR 105/2.8: again a very good choice including VRII. But in many cases simply not long enough (esp. if you think of a FX-body)
- The
Tamron or Sigma 180/3.5 macro: nice but not overwhelming
- The
Nikon 135/2.0 DC: excellent sharpness plus Defocus Control plus f/2.0 aperture. But only 1:7.1 magnification and 50% more expensive
