If you look at Haavard's blog on the Opera site, you will find a reference to run of the SVG 1.1 Test Suite on IE9. In contrast to Microsoft's SVG test suite (of about 104 individual tests in 7 areas), the W3C's test suite has 275 tests, each of which typically has a dozen or so subtests. On the standard test, IE9 passed 28.36 % of the tests. All other browsers are above 60%. Once SVG becomes viable, I expect that all of the other browsers will quickly advance into the 90%+ range. Opera is already well above 90%. So I welcome IE9 into the SVG crowd, but they are far behind the competition.
A skeptic, that is to say, anyone who can recall Microsoft's behavior over the past 20 years, might wonder if Microsoft ran the official SVG test suite on all competing browsers to find areas where they failed. They then built a second test where they know the others will fail. The developers then focused on implementing them correctly in IE9. This would give them bragging rights when they ran their specially crafted SVG test that focussed on these areas. But it would not help improve interoperability if they grade themselves on a new test, rather than the W2C test suite. I hope I a wrong, but like the little boy who cried wolf, Microsoft has a history of misleading the community.
1.79 x 10^12 furlongs per fortnight -- it's not just a good idea, it's the law!