Is it possible for non-BDSM relationships to learn anything from slave-master relationships? I am interested in research on slave-master relationships within the BDSM spectrum. 
This questions concerns people who do not just engage in BDSM recreationally, but rater  define their relationship by this type of relationship.

Master-slave relationships is one of reciprocated devotion and requires much forethought in planning activities. This includes both psychological and physical punishments,  play and games. Many people take their roles in their relationship very seriously. There are clearly defined rules and boundaries that must be respected. This is held in high regard amongst the community. 

Is it possible for non-BDSM relationships to learn anything from slave-master relationships?
BDSM relationships are generally very clear on the respective roles of the individuals. Thus, they provide a refuge from the "war of the sexes" that is being fought in most non-BDSM relationships.

In non-BDSM relationships today, men and women are usually extremely confused about their roles. Men and women both have difficulties accepting women as (co)providers; both partners are expected to partake in child-rearing and household chores, which does not relieve one partner from the tedium of the job, but double the stress by leading to conflicts and an unclear diffusion of responsibility; sex is a minefield where men are afraid to "use" their women, and women can no longer "let go"; etc.

BDSM relationships are reactionary in that they return to the clarity and emotional safety of pre-feminist relationships, only without the patriarchal roles. As both Skippy (user3267) in her question and MingYue in his answer have described, BDSM relationships are often less about specific forms of sexuality, but about a specific from of relationship: one with clearly defined roles, and both partners being able to relax and be themselves in the secure knowledge of what is expected of them, how to behave, and where the limits of their agreement lie – because every relationship is a contract, only non-BDSM relationships make the mistake of tabooing this fact and clogging the free flow of an honest exchange with a thick layer of romantic spirituality.

What non-BDSM relationships can learn from BDSM relationships is to communicate clearly, to define the roles of each partner, and to stop feeling guilty about not loving in a politically correct way. Equal rights don't apply inside the bedroom.



Since there has been some debate concerning the dangers and pathology of sadism, I would like to append a paraphrase of a section in a textbook on sexual deviance (Fiedler, 2004, p. 267f.):


  Research has shown that an inclination to sexual sadism is a mostly safe and harmless preference. Practices of sexual sadism are usally performed with the utmost caution and care, so that injury or trauma is extremely rare (Scott, 1983; Weinberg &amp; Kamel, 1983).
  
  Studies with persons egaging in sadistic practices with their partners have repeatedly found that these persons are socially well integrated, valued by their friends and neighbors and successful (Spengler, 1977; 1979; Scott, 1983; Moser &amp; Levitt, 1987; Baumeister &amp; Butler, 1997). Some authors attest that the social adjustment and psychic health of individuals engaging in sadistic practices with their partners are above average.
  
  Since an inclination towards sexual masochism is about four times as common as an inclination towards sexual sadism (Baumeister &amp; Butler, 1992), we may conclude that some persons practicing sadism in their relationships are not sadistic at all but rather complying with the needs of their loved ones.
  
  In sum, a majority of persons performing sadism in their relationships have no psychological disorder.


Sources:


Baumeister, R. F., &amp; Butler, J. L. (1997). Sexual masochism: Deviance without pathology. In D. R. Laws &amp; W. T. O'Donohue (Eds.), Sexual Deviance: Theory, Assessment, and Treatment (pp. 225-239). New York: Guilford.
Fiedler, P. (2004). Sexuelle Orientierung und sexuelle Abweichung [Sexual Orientation and Sexual Deviance]. Weinheim: Beltz.
Moser, C., &amp; Levitt, E. E. (1987). An exploratory-descriptive study of a sadomasochistically oriented sample. Journal of Sex Research, 23, 322-337.
Scott, G. G. (1983). Erotic power: An exploraton of dominance and submission. Secausus, NJ: Citadel.
Spengler, A. (1977). Manifest sadomasochism of males: Results of an empirical study. Archives of Sexual Behavior, 6, 441-456.
Spengler, A. (1979). Sadomasochisten und ihre Subkulturen. Frankfurt: Campus.
Weinberg, T. S., &amp; Kamel, W. L. (Eds.) (1983). S and M: Studies in sadomasochism. Buffalo, NY: Prometheus.