Short summary for people:
RX 580 vs 480:
Boost clock 1340 vs 1266 (+5.85%)
No change in memory clock
RX 570 vs 470:
Boost clock 1244 vs 1206 (+3.15%)
Memory clock 7000 vs 6600 (+6.06%)
Also, the slides claim "3rd Gen FinFET 14" whatever that means. As well as "enhanced idle & multi-monitor efficiency"
HEVC H.265 4K encode/decode being touted as well.
We'll see about any efficiency changes. Anyway, woefully disappointing coming from the Hawaii rebrand.
390X vs 290X:
1050MHz vs 1000MHz (+5%)
6000 vs 5000 memory clock (+20%)
8GB vs 4GB (+100%, although there were rare and pricey 8GB 290X)
390 vs 290:
1000MHz vs 947MHz (+5.59%)
6000 vs 5000 memory clock (+20%)
8GB vs 4GB (+100%)
At least if AMD made 9 Gbps standard on the 580 it could claim to be reasonably close to their last major rebrand. Heck, 8 Gbps standard on the 570 would have matched the relative increase that 390 saw. But they didn't do these changes. Underwhelming, especially with many 470s already with 7 Gbps and factory overclocks.
The efficiency changes could matter, but they don't look to be for gaming. AMD GPUs have high multi-monitor wattage, so this could nice though. Hopefully they also tackle blu-ray playback wattage, which is high (for the 2 people that watch blu-rays through their PC).
No complaints about 560, btw. Nice to make 16CU and 4GB standard. I assume this means it'll be 1x6pin standard, but that's fine since the new 550 will be for the low power, entry market.