While some have produced some nice shots, there are a lot of complaints about this lens. It seems to have the worst quality control of any lens that I've encountered in my decades of still and video photography (based on my memory, and figuring we didn't have an internet to complain about lenses back in the 1980s.)
If you've got a lens that is consistent and doesn't require two hands to zoom, congratulations! I hope it gives you years of service and that it doesn't need repair after the warranty (which seems to mean you'll just get a refurbished model at a discount, according to some posts).
And if you go to sell it (once Oly's telezooms come out) that your copy will fetch top dollar. I'm sure there are people who tolerate a stiff zoom now and decide they will want to switch (to Oly), and may end up dumping their lens without disclosing the stiff zoom or other issues.
I think it's important that anyone considering purchasing this lens be aware of:
- stiff zoom
- poor quality control/copy variation
- upcoming Olympus releases (which may result in future discounts and a decrease in the resale value of the used Panny.
- the importance of trying the copy before buying to assess whether you can accept any shortcomings on a lens at this price point
- the importance of buying it with a return policy that you can agree to
- Panny's policy about service after the warranty expires which, some have said, results in a lens that's disposable after three years.
After owning four copies, Panasonic told me it's a great lens and that I should keep trying to find a good copy. Which I did. Three times. I just didn't want to damage my body with the metal shavings issue. Perhaps my atandards for an $1800 lens are higher. But at least I get great images from my Oly 75-300, Panny 100,-300 and Sigma 150-600mm (and Metabones converter).

Killdeer with Sigma 150-600mm

Oly 75-300 or Panny 100-300.

This may be the first copy I had of the Panny 100-400. Can't see the EXIF on my phone.
Happy shopping and shooting everyone! It's nice to see good images no matter what tools created them.
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I believe in science, evolution and light. All opinions are my own. I'm not compensated for any of my posts. Can you honestly say that?