I can tell you from my experience, Android is not as polished nor as "organic" as iOS. It's somewhat tedious to deal with and the UI is not as well thought out. Sure, you can customize it with widgets, but it literally takes a second to launch a full-blown app so I never felt the need to clutter my homepages with crippled apps. My homepage was set up pretty much like an iPhone, with a bunch of apps. If you don't set it up that way, you have to tap the apps button to access your apps, adding another layer.
Then there are the little things, like the back button's inconsistent behavior; a major faux pas in UI design. For example, it can take you out of a popup, then back a page within an app, then back to your homepage. Apple's "x" to close popups and back buttons clearly labeled within the app (eg., "playlist") is a much more user-friendly approach. Sometimes, tapping on the back or home button lights them up like they've been activated, but nothing happens; they should be greyed out when unavailable. On my HTC, I also had a menu button that rarely worked which is why Google eventually did away with it.
Using the notification center to see all my activity was never as useful as glancing at my iPhone's homescreen and seeing the badges that immediately tell me I have 3 messages and 11 emails, for example.
Then there are the bugs that required me to reboot regularly and one in particular that made me almost pull out all my hair... I couldn't load web pages and it would happen randomly.
It's not as responsive and the graphics often 'stutter'... much more so than iDevices. This is well documented, and even the latest devices don't feel as buttery smooth as iOS.
As for upgrades, I never received one because Sense UI took up too much memory. And my phone was considered top of the line when I bought it and after only 6 months, my phone wasn't even supported!
So there's a reason why Android comes dead last in every customer satisfaction survey. As for the folks who think Android is all that... the vast majority of them never used anything else so of course it's going to feel revelatory next to a feature phone or blackberry... a good chunk of the Android experience is based on iOS, after all. That said, if you love to tinker and customize every aspect of your device, Android is really good for that.
Thanks for the in dept experience. I can really see the little annoyances and inconveniences of Android that iPhone users take for granted. I think iPhone ESP after hearing about android is really really intuitive and like they say it "just works." No mess, no lag; I couldn't imagine tapping a button to access my apps. That right there is 1 of many deal breakers. Or pull down the notification bar to see my messages and emails haha! I know android folks talk about iPhone UI as being "sooo basic bla bla" but what's the point of a UI with more features but is inconvenient and I'd even say tedious to use on a daily basis....