This weekend I had the privilege of trying out Nikon's long-discontinued 70-180mm micro zoom lens.  For those of you aren't familiar with this lens, it's unique in the world of photography, as it is the only macro lens that's a zoom -- NOT a zoom lens with macro or close-focusing capabilities.  It is also unique in that the aperture does not change as the focusing distance changes.
 

Unlike many of the lenses being produced today, this lens is built like a tank, with an all-metal lens barrel and an aperture ring.  It doesn't have an ultrasonic motor built-in, so entry-level Nikon cameras like the D3300 can't autofocus with this lens.

Roland's Nikon pages and Ken Rockwell list these specifications:

• 18 elements in 14 groups
• 9-blade rounded diaphram
• Diameter: 75mm (3 inches)
• Total Length: 175mm (6.9 inches)
• Weight: 1010 grams (2.22 lbs.)
• 62mm filter size
• Max. reproduction ratio at 70mm: 1:3.2
  Max reproduction ratio at 180mm: 1:1.32
• Manufactured in Japan from 1997-2005, less than 20,000 were produced
   

 For more information on this lens and its development, check out the Thousand and One Nights article here.
On a medium-resolution camera like a Nikon D3 the performance is amazing:

Performance is also spectacular wide open:

The Internet has cast a lot of doubt about the performance of "older" Nikkor lenses on high-resolution APS-C (aka DX-sized sensor) cameras.  On the 24 MP D7200, performance is equally amazing:

Compared to the prime macro lenses offered by Nikon or other manufacturers, this lens has three drawbacks:
 

1. Slow, shifting aperture, making this lens a little slow for normal photography.  Prime macro lenses are usually f/2.8 or f/4.  While this might not be important to some, many people carry macro lenses rather than regular lenses, so this may be a deal-breaker for some users.
2. Maximum reproduction ratio of only 1:3.2 at 70mm.  Maximum reproduction at 180mm is 1:1.32.  Most other modern macro lenses are capable of going to 1:1 (life size).  To get to 1:1, an extension tube or close-up lens is required.
3. Autofocus is slow compared to the current AF-S macro lenses like the 105mm VR.  It's more than acceptable if you're making small corrections, but painful if you have to go from one end of the focusing range to the other.
    

Based on my limited time with this lens, the convenience of the zoom function far outweighs these shortcomings.  Not having the aperture shift as the lens is focused closer is a HUGE help, especially on older camera bodies that don't have an electronic aperture display.  On that note, I should point out that with other macro lenses that have a maximum aperture of f/2.8 -- like Nikon's recent 105mm macro lenses -- the wide-open aperture slows to f/5.0 at 1:1, so this lens really isn't "slow" for macro use.
 

IMHO, this lens is a great buy for any photographer who does a lot of macro work and requires some working distance between themselves and their subject.