It's certainly better than the 4. Obviously the difference in 4 to 4s isn't as great as 4s to 5. If I was already dropping $400, I'd just pony up and get the 5. That or I'd make do with an older iPhone until I was upgrade eligible.
Wrong 4 to 4s is huge compared to 4s to 5.
CPU
4-4S. Single core CortexA8 to Dual core CortexA9. Gaining multithreading from single thread architecture jump is massive.
4S-5 is just one dual core to a another, substantial, but mush less.
Camera
4-4S. Big, 720p to 1080p video. 5 lens system. Panorama. 5MP to 8MP.
5. Lens cover with more scratch resistance and purple light halos
Display
4/4S/5 All retina
5 taller and less ergonomic
Cellular.
4: single antenna, 3-5mbps 3G
4S: dual diversity dynamic antenna system 8-19mbps 4G
5: dual diversity dynamic antenna system 40-60mbps LTE
The 4 already has double basic home DSL bandwidth, 4S even more. Who needs that much on a mobile, really? Silly overkill.
Dock connector
5: Lightning. Losses compatibility with many accessories and all your previous charging cables. Can be hard to bum a quick charge.
Built quality
4/4S strong stainless steel frame, gorilla glass type outer
5 soft aluminum with easy wearing anodization
4-4S Siri, 3D maps, turn-by-turn
4S-5 nothing else.
Take it from a 5 owner who's girlfriend and coworkers have 4S. 4S to 5 is piddly upgrade.