Talk about opening a can of worms. LOL! :lol:
I wouldn't want to use a 1/2-inch seam because of the bulk. It becomes an issue when quilting and I do a lot of hand quilting. Because most patterns, esp. the complex ones, are set up for a 1/4" seam, you may find you have to redraft a lot of patterns and the ones that it really matters on are those patterns that use lots of points. I typically rarely use a 1/8-inch seam because if there is any fraying of the fabric at all then I loose what little seam allowance I have and that means the quilt is likely to come apart if someone sits on it, cuddles with it, or washes it a lot. I know a lot of us had issues with the 1/4-inch seam when we first started but you will quickly get used to it and it won't seem so strange. Plus, using a 1/2-inch seam line means you will end up loosing a lot of fabric in the seams, especially if you make a large quilt like a queen size. With the price of fabric today, I just can't do it!
I learned from a national instructor that I highly respect (Beverly Hindman, who is known for her hand applique & piecing) teaches that unless the block is smaller than 3-inches, you press your seams to one side or the other. I worry less about whether it is pressed toward the light or dark, though I press to the dark if it doesn't matter. I'm more concerned with ease of piecing & block construction and if that means I need to press my seams to the light side of the fabric, I do so. However, a neat little trick to help with any shadowing issues is to trim the dark fabric in the seam just a smidge so that it isn't even with the light fabric. This sounds like it wouldn't work but it really can help get rid of any shadowing.
Hope this helps.