Someday, when I'm drunk
D&C 89 began as special counsel for our day, and has morphed over time into a kind of Christian Kosher. Someday, we may have official Talmudic intepretations of the law, perhaps finally justifying why we may drink Coke but not coffee (though Jim F. has thoughts on that topic). But I don't view the Word of Wisdom is a permanent fixture, nor do I believe that it directly concerns issues of morality the way our other commandments do. As a result, I frequently get the impression that the WoW will not continue in its present state.
D&C 89 is addressed to us particularly in the Latter Days, "in consequence of evils and designs which do and will exist." This suggests to me that it is a reaction, a protectionary measure rather than a series of eternal laws. In particular, the section responds to concerns of poisoning and of indebtedness to Gentiles for alcohol (much has also been made of the folk legends involving chewing tobacco at the School of the Prophets). When these concerns are no longer an issue, will we see a return to the use of, say, alcoholic beverages within the Church, using "wine of our own make" (moonshine)? Would it affect the heart of D&C 89 if current interpretation permitted the drinking of a glass of wine a day, for instance? No -- in fact, this would go with the overall message, that of moderation.
The WoW has impacted my life for good and bad. I suspect that I will never enjoy cocktail parties or hanging out in bars. I had the pleasure of being the designated driver every weekend in high school. I also linger in the coffee aisle in the supermarket, sniffing the forbidden beans. Living in France was challenging, because smoking and drinking are national pastimes. Lately, my drinking, smoking friends can still run faster and further. I run and am weary. But yes, there have been treasures of knowledge I've enjoyed, being free of chemical dependency and being set apart from the world. It's been a great choice.
What does that choice mean? Does the Word of Wisdom involve issues of moral gravity like other commandments? I think the answer is no. Drinking coffee cannot be compared to adultery, theft, idolatry, or any other commandment. I believe the closest cousin to WoW transgressions are those of Sabbath-breaking, which seems a commonplace sin (a "péché mignon," as the French would say). It seems odd to me that it can keep you out of the Temple, because I don't see how those dietary rules affect our souls in the same way as these other laws. The best answer I can come up with is that D&C 89 is a very effective measure of how we obey laws we do not always understand. It is an Adamic form of sacrifice in that respect.
If we are to look for eternal structure within the Word of Wisdom, I would suggest that we should look to its spirit of moderation and the counsels of a healthy diet. I feel that it is pointless for us to talk about tannic acid or biblical fruit juices or caffeine or mitichlorians or any similar rationales for the diet as currently interpreted. We do these things to try and form a solid, immutable structure around a commandment that was given in our day, and was shaped and moulded by revelation -- but D&C 89 remains inherently a matter of practice rather than of theological intepretation.
Others here have highlighted how the WoW has afforded them health, strength and spiritual confidence, and I believe the promises made in the WoW are true. That said, in my opinion the particular diet mandated by D&C 89 is not an eternal concept. The scriptures indicate that Jesus will return to partake of wine with his disciples, so we can say that D&C 89 will not last indefinitely in its current state.
Anyways, what this boils down to is this: I keep the Word of Wisdom because it is a commandment, and part of the practice of a believing Latter-Day Saint. I don't know why we necessarily need all of it, outside of the general principles it contains, but I obey it and enjoy blessings from obedience and from a healthy lifestyle. And when I can drink, I plan on drinking this.
And here is a link to some amazing anti-alcohol posters from the Soviet Union. They are an artistic leap ahead of Mormonads, yet a mere half-step away from For the Strength of Youth.