1. Many iPhone 3G/3GS users never upgraded to 4. This is their chance.
2. iOS5 has many compelling features. Us techies forget that the average joe doesn't really understand upgrades, versioning, etc. Phones are sold as both a hardware and software solution and so many of the iOS5 features are inherently see as being a feature of 4S and not just a feature of any iOS device.
Many of the tech blogs are looking at a technology aspect (RAM oh my!) and not towards how the common man thinks and acts.