It is interesting that you make this comment, because I was just working on a sort of personal challenge to myself by writing a Harry/Draco fic, a pairing I would never normally touch (I adjusted it by making it adjut Harry/Draco and turning Draco into someone I could actually enjoy writing) and part of the reparte was on the "I despise you" line before they got to it. And I'd just stopped writing at the kissing stage, because I love a good tasty kiss, writing wise.

No, it shouldn't be bypassed. Sex can be as much about dominance and combat as anything, and imposing the mouth on someone else can be a real rush in a story. I have only so far written two Sirius/Severus, but you take a look at http://home.iprimus.com.au/amacker/HPThingsIDo.htm as it does have them kissing. I don't know if you'd consider it believable, but my characters seemed to enjoy it.

I'm also in favour of nipple play. More nipples in fic, I say!