After Effects is used in many feature films. It's used together with other tools to create and/or composite elements in a lot of visual-effects-heavy movies (like
Sky Captain and the World of Tomorrow,
Stranger Than Fiction), but it's also used to composite together elements in movies that you don't think of as being visual-effects-heavy. The Emmy award winner for visual effects was
John Adams. Very little in the background in that movie was real. And that was done with After Effects and Photoshop. This year's Academy Award winner for animated short also used After Effects. And, of course, it's used for a
lot of title sequences and closing credit sequences.
Yes, they do. Anything from storyboarding to masking to final color corrections and, most importantly, pretty much any of those fancy mock UIs on screens in movies and TV series is either done completely in Ae or at least involved using it somewhere along the way... Also, many opening animations and credits are done with AE...
After Effects is also used quite a bit in major Video games. I am the Senior Video Editor / Compositor on the Tiger Woods PGA TOUR 10 franchise (Xbox 360 / Wii / PS3 / PS2 / PSP) and I use After Effects CS4 extensively for compositing video assets.
Hey...it ain't Feature Films, but it ain't "low end" either (hate when people refer to AE as "low end").