The ability to whisk away notifications is great.
Here is a huge win for the Pre, that bottom notification bar that I mentioned previously? Well not only is it handy to access, but for items that you only need to see pop up, and do not need to "click through" to read, a simple left to right swipe with your finger across the notification itself sends it away.
This is useful for all kinds of things, short text messages, repeated IM conversations, e-mails that I want to ignore. More recently, I figured out that I could set alarms using the clock application. The only downside seemed to me that an active alarm kept a small bell on the notification bar. Well, once I figured out the full power of the sweep gesture, that bell lived no more. Simply tapping on the alarm bell brought up the alarm notification and then I sent it packing for good, never to clutter up my screen again. Wonderful.
Beyond the usefulness of it, swiping away notifications also brings about a sort of psychological pleasure too. You get to act dismissive and aloof and since it is only your phone, it cannot be insulted. Good feature, Palm, and great utilization.