You might remember my post awhile back about Unrelenting Teenage Angst (UTA) and my hatred for it. Well, I mentioned in the comments on that post that there's also a concept called Unresolved Sexual Tension, or UST. You can also call it Unresolved Romantic Tension if it's more audience-appropriate.
The difference between UTA and UST is that sexual tension, when included properly, can add flavor to an otherwise flat story. The key phrase here is, of course, "included properly." There are some works (i.e. certain romance novels) which are all about the will they/won't they vacillation, and become overwhelmed with the question from dwelling too much on it.
The kinds of works I prefer (and attempt to write) are the ones where the sexual tension is strong but not the overwhelming driving force behind the story. Does that mean all romance novels are sappy, overwrought vehicles for bored housewives? Not by any stretch of the imagination. Granted, I've read precisely one romance novel in my lifetime (I Thee Wed by Amanda Quick if you're interested), so my knowledge is woefully inadequate.
For my money, UST is best when you can sense it between two characters every time they're "on stage." Think Willie and Indiana Jones in Temple of Doom or Ron Weasley and Hermione Granger in the Harry Potter books. Particularly with Ron and Hermione in the later stories, you can sense the depth of feeling between those two characters that leaves you simultaneously joyous and relieved when Hermione up and kisses Ron in the middle of Book 7.
How about your own works? Is there a pair of characters that argue like cats and dogs but have a bond no one can break? Or is romance something you don't really concern yourself with in your writing?