Same for me, although there is some slowdown compared to iOS 7. I am extremely impressed with the longevity of Apple phones in general, and my 5 in particular.

depends on what your definition of 'fine' is. I also use an iPhone 4S with iOS 9, and looked at how fast iOS 9 runs on iPhone 6S and iOS 8 on a friend's iPhone 4S. I don't think I'd call it anywhere close to fine.

I'm numb to the slow response times, but the crashing applications make me want to ditch this for a 50% cheaper android phone which runs faster, and doesn't have planned obsolescence[0] (the link talks about planned obsolescence in iPhone 4S and iOS 9 )

Now I'm okay with most of the stuff apple does with it's walled ecosystem, and appreciate some, but this is going directly against a consumer.

[0]: http://www.digitaltrends.com/mobile/iphone-4s-planned-obsole...

If the updates would contain only security measures - but they don't. So I rather have an "insecure" device instead accepting an update that makes me want to throw the previously satisfactory device into the wall.[1]

But this is also not an option on iOS, because of the apps support and you have to update eventually.

[1] https://www.youtube.com/watch?v=9J6R0NnqOzc