Question on the Canon EF 70-300mm f/4-5.6 IS USM

[ChasDennis]

I have decided to buy a Canon EF 70-300mm f/4-5.6 IS USM . But I see in the reviews that I read were this lens might have a problem with an issue called vertical sharpness.

How would I know if the lens that I am going to buy has this problem and if it does who do I send it to to get it fixed?

I know this sounds like a very basic question but that is because I am a newby and just learning.

Thanks for any help

Charlie

[OsmosisStudios]

What are you referring to with "vertical sharpness"? That's a strange term.

[Elmo]

I like my copy. I use it more often than my f:2.8' zoom in that range

[RichardTaylor]

I am very happy with mine also.

[taschrief]

I believe early copies of this lens had some problems with the IS in mode 1 when in the portrait position. I have had my copy of this lens for about 15 months and have had no such problems with it. The attached was shot at ISO 3200 at a night football game in portrait position. No problems here.

Edit: Once again, my attached photo did not show up. Can anyone help with this?