Same, but I do like one 'main' chair, like a captain's chair. For that throne-like feel at the head of the table.

Mixed is fine. I currently have all the same.
The picture posted as an example is a poor mix of styles IMO

A mix can be very interesting and unique, but it makes the selection much harder.
Read this interesting post:
http://katyhahndesigns.blogspot.co.il/2012/06/mismatched-dining-chairs.html

I like symmetry and uniformity.

I agree with Christie. Mixed but not all keeps things interesting but not distracting.

I think it's a huge difference whether you casually collected the chairs over the years or bought them to 'create' a mixed look. The latter has become a trend, which I utterly dislike.

It depends upon the ambiance you want to create in the space. Mixed tends to be more informal, matching is traditional.

I have 8 matching dining chairs, two that have arms and six side chairs, and I'm changing the rush seats to upholstery. I'm thinking of covering the arm chairs with a different but complimentary fabric than the side chairs. Am feeling a little nervous about this.

For me, I like continuity (but do love the look of different "host chairs"). That is my favorite look.

Here's a picture of the room, and the fabrics I'm thinking of using

I like doing all the side chairs the same and the arm chairs different.

The side chairs would be the brown color, and the arm chairs the circle pattern. But not sure if they are too different. Maybe I need to use a similar weave pattern to the arm chair, but just a different complimentary color?

as long as they are the same color

I don't mind mixing them; just not the ones that are put together in the post; styles are too different.

Sometimes, but not these pictured.

I like mixed but only at the ends of the table where I want the ends to match and the centers to match

Matching side chairs with different styled arm chairs at table ends can work well to create a unified yet interesting look. The styles need to relate to one another, though. Could do upholstered side chairs with non-upholstered arm chairs at end.

No to the mixed. Looks like a mishmash.

I guess it depends on the mix. I have mine the same. The dinning room has the end chairs taller, but the same model and same fabric. Breakfast area has all the chairs the same.

mixed chairs looks cheap. like people have donated chairs to u .YUUUKKK.

i was forced to do mixed chairs but i like the result. i bought 6 brown leather-cushioned chairs with a rounded wooden back and then bought an 8-10 person table. they didn't make my original chairs anymore when i went back to fill out the table.... so i bought 4 grey upholstered chairs with a similar shaped back and then interspersed the two sets of chairs.