See, I definitely remember the WoL campaign being really fun, and really cool to play. Something about HotS's campaign isn't impressing me in the same way yet, and after Diablo 3, I'm starting to question whether I imagined WoL's campaign quality. >_<
I think one thing which annoys me about the HotS missions so far is that I feel they basically tell you exactly how to play them, with voice overs and highlights on the screen and so on, and as long as you follow exactly what is said, you basically can't lose. It feels like autogaming and I hate that. It also feels like I'm just interacting with a storybook, rather than playing a game with actual options. Most of the time I don't see any variation in terms of strategy.
Played about 7 missions so far. I'm actually looking forward to replaying some of the previous missions for missed achievements because they sound more challenging than the actual mission objections (including the bonus objectives which I always get). I'm not even looking for a hard game here, since I'm not that good with RTS games anyway, I just don't want to feel like I'm following exact instructions all the time.