While I don't own a WP7 phone, I can speak towards the platform as a UI designer. I've done a lot of research into the platform simply because I need to be familiar for browser testing and the like. Here's the abridged version of what I know...
Variety of applications:
iOS > Android > WP7 > BB
- It's no secret that iOS has by far the most apps on the market. Many free, many more paid. However, it's a close call for two reasons: First, Android can install any app it wants from any source and second, After a few thousand apps it's all redundant. WP7 actually has more than Blackberry if you don't count their new OS which runs Android apps.
Flexibility of OS:
Android > iOS > WP7 > BB
- Android can be rooted, modified, warped, destroyed. You can do whatever you want to it on most handsets. Unless you want Honeycomb, then things get really iffy. iOS takes a lead over WP7 because there's a pretty solid community of people who unlock iPhones, giving you some of the flexibility of Android (though not nearly all). WP7, the jury is still out. Blackberry... Ugh.
Stability of OS:
iOS > BB > WP7 > Android
- iOS is pretty rock solid, but you'd expect nothing less from an OS as locked up tight. It's also officially the most secure (thank you NSA). WP7 actually just barely edges out Android, even though it's younger. Again, the more locked-up nature of the OS helps.
Quality of Mobile-Web Experience:
iOS > Android >WP7 > BB
- Right now, iOS has the best mobile browser on the market. Android is a very, very close second. It's only because iOS tends to have the absolute latest versions of Mobile WebKit running that it edges Android out. I know some people are going to call fowl over no Flash where it's on Android but I'm sorry, Flash on mobile does suck and contrary to what some might imply, you don't need Flash anymore except for a very limited number of the major sites. I came across one the other day, the first time in months and thought, "No HTML5 at all? Wow, that's just sad." WP7 takes a step back because it's running IE9's mobile version. It's good, but not as good as WebKit. BB's sucks, by the way.
Cross-Platform Support:
iOS > WP7 > BB > Android
- iTunes on Macs and PCs. iTunes on PCs isn't the greatest but it's there and it works as expected. WP7 actually has a pretty solid beta client for Macs as well. Blackberry has some solid third-party developers who are filling the gaps. Android sucks on cross-platform. It's passable on Linux, OK on Windows but barely existent on Macs and what's there leaves a lot to be desired.
As I said, this is the abridged version. The general conclusion is I still think that for most users (especially those who aren't very technical and aren't going to get the full benefit of Android) iOS is currently the better mobile OS. Android is probably the second best and rather close behind. There are areas where iOS is markedly better but there are yet others where Android wins. If you're a technical person, don't have a Man and like to mess around and customize your gadgets, Android is your best bet by far.
WP7 is the interesting, though. It's very young but wow is it polished. I give it two years before WP7 has a good showing in the mobile space, if it starts to take off. Everyone I've talked to who has it, everyone who's seen it, we all are very impressed. Normally, I think Microsoft is horrible at UI design and normally they are. However, somehow they came up with the WP7 OS and it's a work of art. It's simple, intuitive and beautiful. It does take a bit of getting used to but it's not a hard learning curve. Once you figure it out, things just kind of flow from there. I'm very impressed and hope Microsoft keeps pushing it. It's about time iOS had some really polished competition that had a unique UI.
Blackberry... If you bought one of these you were either told to by your work, you didn't know anything about phones, or you have a lot of friends who have them and want to be on BBM. Otherwise, you'd be crazy to buy a BB. Why? Let's put it this way. The day before the first iPhone was announced, RIM thought it was impossible and the rumors were just that. They were a little vocal about it, too. But then, the next day, the iPhone launches. RIM panics. They have four all-hands meetings THAT DAY. Not to figure out how they're going to stay in the lead, not to figure out what their answer is going to be... Four meetings to answer one question: "How the heck did they even pull that off? It's not possible! Right?" They're still trying to figure it out.
Oh, there's WebOS as well, which is quite possibly the coolest of all the mobile OS around. However, it's barely made a blip. It's too bad, I would love to see some proper WebOS devices. Though, where WebOS is going to beat out the others is it takes full advantage of web tech on the OS level. It's recently been bought by HP so we'll see what they can do with it in their upcoming tablet.
OK, that's probably more information than you wanted but hopefully you'll find it helpful. If you want specifics on any of the points let me know.
