A really, really annoying bug (if you want to call it that) is the overlapping of ambient dialogue and quest (or interaction) dialogue that sometimes appears.
The ambient dialogue is getting really annoying in general.
It's not a bug, but I think it's something that needs to be altered in a future patch. Lower the frequency of the one-liners. I don't need to hear one every single time I approach an NPC, especially since it's the same lines being spoken over and over.
It gets especially aggravating if you remain near an NPC. When they run out of things to say, they go into an endless stream of lines like 'Yes?' and 'I'm waiting!' and 'Do you want something?' It's most noticeable from the Altmer merchant in Windhelm while you're using the enchanting table near her.
When you're simply passing an NPC you've ticked off in the past, and they say 'You want to talk to ME after what you did?!' it's just patently silly.
Ideal would be a check for the player standing in front of an NPC and looking directly at him/her for, say, a second. When it's clear that the player is interested in a chat, start the one-liners. If this could include a check for other scripted dialogue, to avoid clashes, all the better.