It was the first I bought but key features it hit included tethering, stereo bluetooth support, compass (and maybe improved GPS) and performance.

The 5 seems like a solid step. I don't see the need to upgrade every year but if you compare back to the 4 rather than the 4S the performance should be a massive jump. Support for 5GHz wifi could mean a real speed boost too and the bigger screen should be nice.

The S really was the feature. Besides the performance bump for everything (e.g. loading web pages twice as fast) it let you run a class of apps you simply couldn't only earlier iphones (e.g. unreal engine).

Other then that copy and paste and enough memory to keep more then 2 tabs open in safari were what I remember.

For me it was that my original iPhone contract was finally up and I could get 3G. Is that the one with gyroscope? -- Jobs playing Jenga during the keynote?

When 3GS was released, it was an evolution of a 3G that was still at light years from competitors.