I have been using the iPhone for the past 3 years and invested on plenty of apps. I am looking forward to see the new hardware in June, but HTC evo on Android looks sweet. I can't see myself switching because then I would lose all those apps. I would have to re-purchase on Android. Plus, most apps on android are not great. Plus, the Evo is on Sprint. Plus, there is no 4g in most places yet. Froyo sound great, but iphone 4.0 sound great, too. I am more than liking stay with the iPhone.
Please keep us all updated on what you decide, we're all on pins and needles.