[JKT]

Short answer - no.

The WebKit nightlies are 90% Acid 3 compliant, but they are not classed as stable releases. OmniWeb 5.7 will be using the last stable release of WebKit, which is not going to include the very recent updates to WebKit that have improved its Acid 3 compatibility. Once WebKit stabilises again, then OmniWeb will no doubt get updated to that version.