Earlier quoted context omitted.
Is it? I just downloaded this alpha and ran SunSpider. Chrome 4.0.266.0 got 506.8ms +/- 6.6%, Opera got 763.4ms +/- 4.4%.
It might be machine dependent. For me on an AMD Semperon: Opera 10.5 alpha: 700.8ms +/- 0.8% Chrome 4.0.266.0: 840.4ms +/- 4.2%
FWIW I ran in a Core 2 Duo P9500 with W7 64, 4gb of ram.