Lyric from "Bad Case of Loving You (Doctor Doctor)" goes here

So, flist. Am watching New Who, finally (which, in the time it's taken me to get started, has turned not quite so new anymore, hasn't it?). Here's my question for you: which episodes, if any, would you recommend not watching for whatever reason? Episodes that weren't any good, episodes that pissed you off, or any other reason- I am wondering what to skip, but I am also sort of fascinated by what makes people hate an episode.

Please note that I have a place in my heart for all the Doctor's incarnations and all his friends, so "Skip all the episodes with Amy/Nine/Martha/River/Jack/etc in them" is nonresponsive. Assume I'm not spoiled for anything (though I am, for quite a bit of things- when in doubt use blackout text).