Is upgrading to the iPhone 5 even worth it?

I have an iPhone 4 right now. My phone has been getting slower and slower lately and I feel compelled to upgrade, but it almost doesn't seem worth it to me. Aside from Siri (which I can live without), what improvements come with the iPhone 5?

Short answer is no. Unless you have a bunch of money the differences are negligible this time.

I use my phone as a GPS, and the processor in the 5 is much faster than the 4, so it's much more effective. The panorama camera thing is very cool. And the screens load a lot faster. It's noticeably faster. I got my wife one and she thinks so too.