I've had the honor of trying out every major mobile OS on the market for a decent amount of time (at least one month as a primary phone for each OS). Here are my honest impressions on each: 1. Windows Phone 7 - I've been using the HTC Trophy the past month. WP7 is on par with iOS in terms of speed and I much prefer the eye candy of the Zune player to that of the fairly simplistic music player of the iPhone. Simply put, WP7 is a gorgeous UI - the animations are slick and elegant, the typographic-based interface is unique. The only thing holding up WP7 is hardware and apps. Hardware will obviously be corrected once Mango phones comes out in the Fall, and I'm confident MS is on the right track in terms of apps - 20,000 and counting. As of right now though, a non-Mango WP7 phone looks great but there simply isn't enough functionality - no multitasking, no Pandora, mediocre app selection, and an annoying app store layout. However, I can safely say I will be getting a next-gen WP7. 2. iOS - it is what it is. Fast, simple, and app-centric. The entire OS is totally coherent in terms of appearance (like WP7 and WebOS but unlike Android). Unfortunately, iOS is far behind its competitors in terms of the sophistication of the UI, even with iOS 5. Apps selection is obviously the best, and even discovering news apps is very easy to do on the iPhone and on iTunes. Apps are great - the problem is that once Android and WP7 closes the app number/quality gap, iOS has little benefits over its competitors currently. I like iOS but I become incredibly bored after a few weeks using an iOS device. The advantage of simplicity of iOS is the thing that keeps away advanced users who want to be able to do more. There's nothing to do but apps - Android, and Honeycomb in particular have a more computer-eque interface that keeps things interesting. 3. WebOS - WebOS's major weakness is a terrible app store and two years of atrocious hardware. The Pre 3 looks great, but does WebOS have the ability to attract developers and a sizable customer base? I do think WebOS as a whole is overrated - maybe it's because competitors have stolen the best part of WebOS (notifications, universal search, etc), which removes a lot of the WebOS luster. As much as I love the card multi-tasking, I don't think it should be the main UI element of the phone. I think the most intuitive and ideal multi-tasking UI would be a combination of the multitask gestures of WebOS and the layout of Honeycomb in which you could have a software/hardware button to bring up a live carousel of apps running. 4. Android - Android has the obvious advantage of being ridiculously open and customizable. My main problem with Android is that the UI is ugly and not uniform. Android apps simply don't look like they were made for the Android OS. I've owned many Android phones and always hated how the UI/skins lacked uniformity. On the other hand, I think Android has the rest beat in terms on functionality. Voice capabilities are amazing, google maps navigation is excellent, as is google integration and gmail. There is no doubt Google will continue to innovate and add more compelling features to Android, but iOS 5 (notifications), and WP7 (Bing navigation, visual search, etc) are closing the gap.