Should I upgrade to an iPhone 5S?

I bought an iPhone 4 when Verizon first offered service, about 2 1/2 years ago. Everything is working well and it's in great shape. The ON button sometimes needs an extra push. It does everything I ask of it, which, admittedly, is probably not all that much compared to other users. Mainly I use it for calls, texting, check current bus schedules, Angry Birds, some foreign language apps, and snap the occasional photo. I'm pretty miserly about data usage -- I generally check FB, check email, and surf at work or home. I'm using about 30 of the 32GB, mostly with music.

Last night I successfully downloaded iOS7.So far, everything seems to be working.

An Apple store recently appraised my iPhone 4 at $81 for a trade-in. I know I can fetch a higher price elsehwhere, but I doubt it would be much more.

So here's my question: It is worth it for me to upgrade to the iPhone 5S? I don't see how a faster processor, better camera, more memory, or bigger & better screen benefit me much.Am I overlooking something?

Absolutely, as life is chaning so you must change with life.