No problems - cranks up Entourage 2008 about three seconds faster than Outlook 2007 on the UX390N that I have to hand (1.33Ghz Core Solo, 1Gb RAM, SSD, running Vista Business), which happens to be the slowest Windows ultraportable I own. About 5 seconds to crank up Entourage and attach to my Exchange Store ready to sync, as opposed to about 8 for the UX.
The UX is however about a second faster to launch Excel 2007 vs Excel 2008 on the Air, and about half a second quicker in Word. Not an earth-shattering difference, and the Air boots up these apps in what I'd consdier to be a perfectly reasonable time.
It is kind of weird though that the Air is beaten in those two respects by this,
given that MS Office is a heavier-weight application under Windows...
Either way though, not a big deal - pretty much what I expect for an ultraportable, and nicely usable in terms of overall response. As far as performance is concerned, can't complain.