As a general rule, I usually didn't have problems with Trek romances. There are some exceptions, but I'd have to rack my brain to remember some....
Here are my various thoughts:
Kira/Odo: Now...I may be in the minority here, but I think it was pretty rewarding to see them come together. There was a lot of build-up, close calls, etc., and...I feel for Odo, in his struggle to do something about his feelings....
I kinda agree that they "toned it down" a bit too much after they came together. Still...their story in the final episode arc removed any such concers...and their final scene together was excellently written and acted.
Troi/Riker: Good...when we saw it. For the most part, they're just friends. When we see evidence of romance, though, it's pretty rewarding.
Jadzia/Worf: Pretty good. I kinda disagree with Nerys here, in that I rarely saw Jadzia actually diss Worf's values or culture. Recall that she actually sees herself as something of a Klingon.... I'd think this is just "poking fun" on her part. And Worf understands this, hence Ezri's line in "Strange Bedfellows", about Worf finding Jadzia's barbs to be "endearing".
I think they're two of a kind, frankly--or at least, they fit together pretty well. Only a woman like Jadzia could be strong-willed enough to provide an endearing, "invigorating" challenge to Worf--and only a man like Worf could be "warrior" enough to have Jadzia desire to submit to him....
Keiko/O'Brien: Okay. At first, Keiko's attitude drove me crazy--for the reasons everyone mentioned. She was this close to deserving a brand of "whining JERK!"
Eventually, though, the writers wised up, and with "Fascination", they finally resolved this (with O'Brien being victorious, and Keiko putting on the dress, and....) and from that point on, their relationship was a WHOLE lot better.
Kirk/Rand: This one hasn't been brought up, but...I REALLY wish the writers had done something with this. There were so many hints of what MIGHT have been.... *sigh*
Trip/T'Pol: Opposites attract, in this case. Gotta love the irony--the pair that used to hate each other's guts...eventually get together. They have some nice moments, those two--including in the books....
Garak/Ziyal: Good to a point. Wish the writers had developed it more--the man of secrets, struggling not to open up to the girl who sees within him something more....
Worf/Troi: Didn't care for it. There were some nice moments of humor about the possibilities...that was it. Glad it didn't really go anywhere....
Ezri/Bashir: Probably my all-time favorite. The chemistry here was PERFECT! These two were perfect for each other--they complete each other, in a sense.
I think the writers did some pretty nice build-up in eps like "Chrysalis", "Protigal Daughter", and "Field of Fire", where the two, in various scenes, basically help each other out, and build each other up when down. And it's well handeled how they finally come together--their intial awkwardness, their joking "agreement" to stay friends--and, of course, their memorable scene in the turbolift....
I really think, then, that in this case at least, the romantic chemistry DID truly shine. It's a shame their romance was only seen for 1 1/2 episodes....
(And also a BIG shame that Mike and Andy somehow felt the need to...ah, well.... *sigh*)