Well, it's not super big deal, but it is annoying. On the trainon my way to work, I've been listening to podcasts and playing Goblin Sword (excellent game btw). Whenever the train passes by tall buildings or trees or anything else that occludes the sun, the auto brightness changes the screen output and suddenly the game goes in slow motion for a couple of seconds.
Is it the end of the world? Nope, but it feels like an annoyance that could have been avoided.
You're right... it's not the end of the world.
However, just a minor version ago, it didn't happen at all. Also, a couple of versions ago, I could play openGL games without frame drops. Then, since 9.3, these games stutter for me on my iPad (and restoring and setting as new doesn't fix the problem).
Like I've said previously, I have never had this many issues with iOS before iOS 8. Also, something along the way happened to iTunes and syncing is not reliable anymore. I have so many issues syncing music that's locally stored on my computer. My iTunes library is very organized, tagged, and every single piece of artwork is set, yet I still get instances where random songs decide not to sync or songs are in my library, but not in the playlist that it's supposed to be in. Also, I'll think everything is fine, but then a song will skip part of the way through to the next song... it's frustrating... then later the same day, that same song plays fine all the way through! All of this started with iOS 8 and has been frustrating ever since. My wife experiences the same issues (and even some different ones).
So it's not just frame drops. iOS is a mess now. Everything used to work beautifully, but that is gone now.