It was an integral part of ENT from the start, so I have no idea what you mean when you say they added it.
Maybe you're referring to T'Pol's scene with Trip? If so, I think it was high time modern Trek became less prudish. Sexuality is a normal part of life and therefore should be a part of drama, too.
While I agree with the sentiment, the problem is that the de-con scene in the pilot was completely asexual while trying to be sexual. It was two sexually attractive people in their undies rubbing gel all over each other while having a sober conversation about politics and the psychology of a third party. It was ridiculous.
If they were trying to sexualise Trek then they'd get no complaint from me, but they were just just throwing T&A into a regular exposition scene and the whole thing was pathetic.