The only significant change that I'm aware of (regarding SwipeUX) is to enable configuration of which screen is displayed depending on the direction of the swipe. This is an improvement, but is still not enough to lift the overall productivity level above that of Freemantle.
As it stands, from an end user perspective, I don't see much to differentiate this device from the likes of the iPhone..
but the risk that Nokia will cease to repair/replace N9s in the future (i.e. within 2 years of release).
There are already cases where N900 owners have been asked to accept N8/E7 as a 'replacement' for a faulty N900 returned within the 2 year warranty period. I don't see any reason to believe this won't happen with the N9.