I remember how frustrating it was in late 2003 when buying a Mac that was great in every way, except it only had USB 1.1 and then Apple released revision with USB 2.0 only a few months later.
To this day, that machine is severely crippled as a result. There are so many things I cannot do with it. I gave it to my dad so we can video chat with Skype, but the video quality is so poor, even though he is using the absolute best (in terms of picture quality) webcam that has ever been created: Logitech's QuickCam Vision Pro. It's a USB 2.0 webcam, and the drop in bandwith due to the USB 1.1 connection on the Mac negates any positives of this camera. (A girl I'm dating uses the exact same camera with a USB 2.0 connection, and the picture quality is by far the best I've ever seen for a webcam).
A common topic of discussion on this forum is the pros and cons of waiting to purchase. USB 3.0 will be one of those rare monumental leaps in technology. The bottom line should be this: If someone replaces his Mac every year with a new revision, then he should buy immediately. However, if he is one who only buys a computer once every four or five years, he should wait for USB 3.0.