First benchmarks are in and put the 8-core Zen only marginally faster than the 6900k
Blender; benchmark, Zen @ 3.4 Base clock, and no boost matches i7 6900K at stock clocks 3.2 GHz/3.7 Turbo.
Handbrake; it transcodes 5 secs faster than the 6900K. 54 secs vs 59 secs.
The main factor is RYZEN is 95w and the 6900k is 140w. AMD is also rumoured to have Thunderbolt Technology in the next gen of ZEN.
Lets hope AMD is right and we will see some stiff competition for Intel.