It seems the latest preview release of Opera comes pretty close to passing the Acid2 test. Apparently there is only one bug left to fix.
After the initial announcement of the second acid test, a race began to become the first browser to pass it. Safari won by a streak and was followed by iCab* and Konquerer. However, these were internal builds only and since then there has been no officially released browser that passes the test.
Also included in this release of Opera is support for some of the Web Forms 2.0 extensions. I’m sorry to report that this is one ugly implementation. Worse than that, the new controls (date pickers etc) are completely
inaccessible unusable by keyboard. I assume that this will be sorted out by the time this release is final.
*Now in public beta.