Peter Capaldi's first episode, Deep Breath, is a many layered story. The underlying story, clockwork robots from SS Marie Antoinette trapped on earth for an unknown length of time, really takes a back seat to the post regeneration events. It's not the first time that has been done.
Even the title has many layers to it. The obvious is that to fool the clockwork robots, they need to take a deep breath and hold it. But Clara is obviously troubled by the regeneration and needs to take a deep breath and realign herself. And from the description of the series it sounds like Steven Moffat is advising us to take a deep breath because this season is going to move fast.
This episode went by fast. I never wanted to look away. It was filled with good solid story telling. It really centered around Clara coming to terms with how the regeneration turned out. But that would be a boring story by itself. So on top of that they face some nasty robots. the greatest part is that at one point the Doctor correctly identifies when the ship is from, even finds the name, but never associates it with the events in Girl in the Fireplace. A nice hint that at over 2000 years old, he doesn't remember everything. Well, he did just regenerate.
I had very little to complain about. I thought it was fantastic and well written. A superb first outing. But, not everything was perfect. I thought the T-rex was too large - unbelievably so - and I really missed getting to see the scene where the Doctor picks his wardrobe. Other than those very minor points, it was fabulous.