I'm very familiar with Sense versions prior to 4 since I've used it a lot. Admittedly, I've only used the One X for ~20min in a store, but have read pretty much all the Sense 4 reviews, and I really don't see where its making a 'clean break'.
The Contacts, People apps, all the widgets, the lockscreen, are exactly the same as in previous Sense versions, with maybe mior changes in the big clock. The settings menus is different, and the apps have a menu button. But the violate the standards too, e.g. apps are supposed to have an action bar, not a list of text buttons like in the gallery/browser.
I want to see evidence of this supposed revolution from earlier Sense versions. To 99% of HTC users, the biggest change will be the customizable dock and the clock. The rest is the same.