Dear SRenee: As you have correctly stated, some of the best studies of "post-tubal syndrome" have not found a statistically significant increase in menstrual problems. Here, from the National Library of Medicine site, is one of the largest studies:
N Engl J Med. 2000 Dec 7;343(23):1681-7.
The risk of menstrual abnormalities after tubal sterilization. U.S. Collaborative Review of Sterilization Working Group.
Peterson HB, Jeng G, Folger SG, Hillis SA, Marchbanks PA, Wilcox LS; U.S. Collaborative Review of Sterilization Working Group.
Source
Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA 30341-3724, USA.
Abstract
BACKGROUND:
The existence of a post-tubal-ligation syndrome of menstrual abnormalities has been debated for decades. We used data from the U.S. Collaborative Review of Sterilization to determine whether the likelihood of persistent menstrual abnormalities was greater among women who had undergone tubal sterilization than among women who had not.
METHODS:
A total of 9514 women who underwent tubal sterilization and 573 women whose partners underwent vasectomy were followed in a multicenter, prospective cohort study for up to five years by means of annual telephone interviews. All women were asked the same questions about six characteristics of their menstrual cycles in the presterilization and follow-up interviews. Multiple logistic-regression analysis was used to assess the risk of persistent menstrual changes.
RESULTS:
The women who had undergone sterilization were no more likely than those who had not undergone the procedure to report persistent changes in intermenstrual bleeding or the length of the menstrual cycle.
They were more likely to have decreases in the number of days of bleeding (odds ratio, 2.4; 95 percent confidence interval, 1.1 to 5.2),
the amount of bleeding (odds ratio, 1.5; 95 percent confidence interval, 1.1 to 2.0), and menstrual pain (odds ratio, 1.3; 95 percent confidence interval, 1.0 to 1.

and
to have an increase in cycle irregularity (odds ratio, 1.6; 95 percent confidence interval, 1.1 to 2.3). Among women who had had very heavy bleeding at base line, women who had undergone sterilization were more likely than women who had not undergone the procedure to report decreased bleeding (45 percent vs. 33 percent, P=0.03).
CONCLUSIONS:
Women who have undergone tubal sterilization are no more likely than other women to have menstrual abnormalities.
As you can note SRenee, the confidence intervals