I just made the switch this past week. It's not that hard. I had all my contacts on either my exchange account or my google account so i they all transferred over just fine. Calendars too (although you'll miss week view). The things i miss the most from the Pre+ i was on are like i said the calendar week view, the notification icons (i know they're fixing the notification system but webOS had it right, apple should have copied them instead of android) the notification LED (you don't notice how much you relied on it until it's gone) and that's about it.
Someone mentioned swipe to delete, you can set this up in your email and it works just the same, it's not as aesthetically pleasing because the whole header doesn't swipe ove, but it functions the same.
I'm on a iPhone 4 and waiting the upgrade to iOS5 which will fix most of the issues that i have with the switch. I'm very happy i switched.