Wow, in all honesty, I can't believe some of you people. Some are angered at Apple for 'patching' this 'security flaw', and others are happy that their devices are now 'more secure'. This wasn't a flaw in the first place, it was a down right lie, and let me explain it to you:
Back when enterprise support was released, users had two device options: the iPhone and the iPhone 3G. At the time, the latest version of Exchange Server was 2007, which supported encrypted device connections. So, even though these two devices did not support such a connection method, Apple decided to 'fake it' for the shear sake of selling devices under the 'works with Enterprise/Business/Exchange' mantra. This was not a flaw, at the time at least, yet a feature: they faked the encrypted connection in order for these devices to be able to connect to secure Exchange 2007 servers.
Fast forward to Wednesday, and Apple released the iPhone OS 3.1 update (3.1.1 for iPod touches). Apple decided that the iPhone 3GS was the device to have, and, without ANY warning whatsoever, 'fixed' this 'bug'/feature, which ended up disabling sync between the iPhone/iPhone 3G and a encrypted connection Exchange 2007 server.
The fact of the matter is this: Apple enabled this flaw/feature in order to sell devices. Let's be frank: at least a decent number of iPhone sales can be attributed to the fact that the devices were compatible with Exchange and enterprise setups. Now, with a new device available, Apple decided to play by the rules and stop lying to Exchange servers, breaking sync for a (potentially) large user base.
They didn't fix a flaw, they simply stopped a lie/fake connection.