Acid2 is the start
Microsoft used to know how to innovate. When they thought they'd won the browser wars, they stopped working on their browsers. However, they hadn't won the war. They'd simply won several significant battles against the weakling Netscape.
Microsoft didn't take part in the first 5 years of the 3rd millennium. Darkness reigned. Microsoft steadfastly refused to do anything to fix the many, many bugs in IE, nor better support the standards.
As with so many other things in the corporate life of Microsoft, they only react when there's competition. They couldn't care less that developers had to spend twice as much time to build a website to cater for their bugs and 'features'.
(see http://tinyurl.com/yz2zaj for the "Breakdown of modern web design")
IE7 simply patched a few bugs and created a whole bunch more.
So now the chickens have come home to roost. The web development community absolutely hate them and have no confidence in them to deliver anything of quality.
ACID2 is just the start of their penance.
The world needs a bug free browser that properly supports the standards. A browser where when bugs are discovered they're fixed, not turned into features.
And an apology from Microsoft wouldn't go amiss for all the wasted hours as web developers tried, often in vain, to get their sites to work whilst Microsoft sat on their arses. The next Microsoft corporate t-shirt should be made of hair.