[Rumor] No SAMOLED and no Exynos for the GSIV (UPDATE: leaked screenshots!)
Also home button, aluminum sides, plastic back, and no pebble shape.
The no samoled thing is kinda good news but if it has the same old shiny plastic back my next device won't be another samsung.
Update: Some leaked screenshots from the phone show a quadcore processor not an octacore one. Also the settings menu uses a light theme that samsung currently uses for its tablets so that might confirm the absence of amoled as well.