I am self-taught and I have been pressing open for 40 years now. It is a growing movement! I think more and more people with home quilting set-ups are finding out the joys of open seams.
I believe that pressing to the side is an artifact of hand piecing during a period in American history when our fabric was rather flimsy and is simply not needed in the modern world with modern machines -- including irons! Electric irons are so much better than heating up a solid bar of metal on top of the wood stove).
Here's a nice breakdown by someone other than me!
http://www.equilters.com/library/tec...SeamsOpen.html
But basically it boils down to doing what you like and works for you. I find I get better results pressing open and using pins. Other people try to avoid pinning at all costs and apparently like those ugly bumpy seams and making little snips here and there to spin their seams. I used to be all about precision but now combine pressing open with modern construction techniques and cutting large and trimming down and I am extraordinarily faster and more precise than my friends who are doing it the old school way.l
Personally, I like having one rule and that is "press open". For you press to the siders, well there is the "usually press to the dark" except when doing this, that or the other thing and I really hate what it looks like when you piece two pieces of white together and get that thick heavy visible bar on one side of the design.
edit: I stitch in the ditch all the time, and when I say in the ditch, yes in the seam line itself and not next to it. Your quilting stitch should be larger than your piecing stitch and I have never had an issue. I typically use a 10 needle and about 12+ stitches to the inch to piece, and a 12 needle with about 10 stitches to quilt with. Oh yeah, I've been using Dual Duty cotton wrapped thread for the last 40 years too. No problems with the seams. I pulled out one of my "use" quilts that is some 30+ years old today to put in the dog bed. Because it was not heavily quilted, the fabric in the middle of the pieces where there was no stitching has rotted out but the seams are still beautiful holding together their edges of remaining fabric.