There is a lot of talk on the web about "bokeh," most of it erroneous/misleading... so I want to address the considerations of bokeh influencing an image.

This is not an example of Bokeh.

This is not an example of Bokeh. (not a very good one anyway)

And this is not an example of Bokeh. 

Bokeh is a lens characteristic as to how it renders out of focus points due to it's design/manufacture (# of aperture blades, optical abberations, vignetting, etc). In other words, a lens has good or bad bokeh, an image does not. The image is a result and *may* show if a lens has good/bad bokeh, much like an image may show if a lens is particularly sharp or not. But only if used in a manner and situation suitable to reveal that.

In an image, "bokeh" is the "quality" of the out of focus areas in an image... it is not shallow DOF. 

But, in order for bokeh to be a factor in an image a few things must exist.

There must be some detail to discern. The first image is not a good example because the BG is blurred to the point that there's nothing to evaluate... This can be done with any lens in certain situations.

There must be some contrast to the detail. The second image is not a good example because the BG is pretty monotone. Without contrast bokeh characteristics do not have a significant influence on an image. This can done with BG selection.

The areas of contrast need to be smaller. The third image is not a good example because the areas of contrast are larger and less distinct. If you have only one large area of contrast then you only have one bokeh "boundary;" and therefore it (probably) doesn't have much influence on the image. This can also be done with BG selection.

Sometime the contrast can also be mitigated with the use of a CPL or positioning.

However, this image is an example of Bokeh. 

This image has many small areas of high contrast in the leaves above the antlers. So now the bokeh characteristics of the lens becomes a more significant consideration. And it's actually pretty crappy (the image isn't that great either; I just don't have many examples of "bad bokeh"). In fact, you can compare the lower sections of the BG where the details are larger/lower in contrast and see a kind of "transition of bokeh" from the bottom to the top.

All of these images were taken with the same lens. 
It's a lens I use a lot. It's a lens which isn't known for it's great bokeh characteristics (and you can see why). But I don't care because bokeh isn't always "a concern," and because "bokeh issues" can often be avoided/managed. I use the lens because it's sharp, fast, and long. And those factors matter more to me. 

And this is why you'll hear/see me say that I don't consider bokeh a primary factor in lens selection... I've never once considered it for a lens purchase. But I can't say that you shouldn't make it a major consideration in your purchases... that's up to you. But you should understand when/why it may be a concern.

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