I always press my seams open because I use a lot of pins to match my seams. Unless pattern specifies to iron to one side like in a Bargello. I love the flatness it gives!

Hadn't thought of that -something to consider. I once had batting that bearded, and I don't want to repeat the experience!

I press to one side most of the time, but there are situations where it makes sense (at least to me) to press a seam open to reduce bulk where many seams come together. It's a judgment call; not a case of right or wrong.

I find that many modern quilt patterns instruct to press seams open, and when the pattern calls for it, that's what I do. Pressing to the side doesn't make the seam stronger, but in a hand sewn seam, it offers some cover for the gaps in the stitching. Often there will be a design reason to press to the side, if you want one area to recede and one come forward. I like pressing to the side, as it does aid in matching the seams, and I just enjoy the look of it on the back. Things seem more solid. And of course, if you want a ditch to stitch in, you have to press to the side.

your quilt your rules

yep. totally situation oriented .

depends on quilt, some quilts use locking seame which they need to be pressed to the side for this, I would look at a quilts design and decide. Bargellos are especially know for having to press a certain way because there are a lot of locking seams to get everything to line up. If you did it open it would be more of a pinning effort to line everything up. Also if you are going to stitch in the ditch I would also be concerned about pressing open, so I would just keep in mind your whole quilt plan before making a decision on which type of pressing you want to do.

For hand pieced seams, you always want to press to the side because that makes the seam stronger. Seam strength is not an issue with machine piecing. The quilters who gasped at seams pressed open did not understand this difference.

As mentioned, seams pressed open can allow batting to beard through the seam. However, this is usually an issue only when doing stitch-in-the-ditch, especially if the batting is polyester and/or the stitch length is not small. Shortening the stitch length (and having a balanced machine stitch; some machines are really poor at balancing the top and bottom threads) can prevent this problem, plus cotton battings are highly unlikely to beard in this manner.

Pressing seams to the side can speed up piecing of certain types of pattern that involve lots of seam matching -- for example, quilts made of 9-patch blocks.

Pressing seams open can help when matching strip sets in patterns made exclusively of strip sets.

For apparel sewing I always press open. For quilts to the side. I tried pressing open but didn't feel good about it so I switched back. I want to have the option of SITD if I want to and not worry about stitching over only thread.

when I first started quilting, I was told to "press to the darker side". Then a few years ago, I saw a gadget demo'd at a qulit show, called a "strip stick". ( http://www.thestripstick.com/ ) To me, this is the best tool since the rotary cutter!! My blocks not only lay much flatter, but they tend to be more accurate (I am very prone to IRON rather than PRESS, which of course leads to distortion.)
With that said, it is still very much a matter of personal choice. Unlike some of the other posters here, I have not had any problems with the batting bearding through the seams. And I have not run into "the quilt police" as someone else did.
Just my 2 cents worth.