Though not a Mac User, I have been using the original iPhone since a week after release. I would be hard pressed to use anything else at this point. I really dig the touchscreen, and can type faster on the keyboard than anything with buttons.
My cousin has the Android, he brought it over last week and I got a chance to use one for half an hour or so. IMHO I like the setup, but I'm not too fond of the keyboard. The OS is a little clunky, and the apps have about two years to catch up to Apple, they just dont have the support yet. Its a great all in one unit for people who really don't want a Mac. He is totally sold on it and uses it for work, etc. I know nothing about the Palm Pre.
The coolest thing I liked about the Android it was the Astronomy app, that centralizes your location by readings from 3 satellites, and then gives you a complete star chart (where you aim or point the phone) with constellations and heads up info about each of the stars. The iPhone doesn't have THAT (yet...
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Anyway, when you get one keep us updated; I'm always interested in hearing about competing technologies.