I totally agree with you, motherofboys. I personally don't think DTD timing does anything at all, but with things like diet (calories, acidity, etc.) I think at the most they raise your odds a little bit. Nothing is fool proof though, and there's some speculation that the man has a lot more to do with it than we think (e.g. certain professions of men have more sons or more daughters, and I also read that men with all brothers are more likely to have boys and men with all sisters are more likely to have girls). Again, I think these are just slight odds -- not any where near 100%
I actually did a large poll in a vegan parenting group I'm in since I read that vegan diets are more likely to result in a girl. (Due to them being lower in calories in general and containing more foods that tend to favour girls.) The results: vegan parents seemed 20% more likely to have a girl, but overall, that's not very high. There were still a few women who had only boys or had some of each, even though the larger trend seemed to favour girls.
I really don't think you should feel bad about something you did/ didn't do when attempting to sway though! It could be that you raised your odds from 50% to 60%, but that's still a 40% chance of getting the sex you weren't aiming for.