Well kind of late to the game here but I'll give you my opinion based on every product I own.
iOS4: Pretty much my whole family has the iPhone 4 and I've got an iPad 2. It's all gravy, no real flaws but nothing too outstanding either. It's just average perfected. The app store is big and unpolluted but I despise using iTunes and the mobile market isn't too great either. No upgradeable storage (save for the iPad) is a big loss for me. I'm not a fan of virtual keyboards either.
Windows Mobile 7: My mother had an LG Quantum for a few months, and it was delightful. Amazing keyboard, beautiful OS (more polished version of the ZuneHD OS, which I fell in love with the day I got one). The only problem with this is the HUGELY empty app market. Also phonewise you get a few options, not as much as I'd like.
Android: Oh my god I love android. I got the Motorola Backflip a year ago at 1.5 and I was amazed, I had previously owned a blackberry curve and I couldn't stand the OS. So I was given the option to either get an iPhone or any smartphone of a similar price. (Easy choice for me, I couldn't stand the aesthetics of any iPhone until the 4th gen, especially the OS) So I got the Backflip, which was a great choice in my opinion,
full keyboard, 5mp camera that can rotate, and a delicious touch panel on the back so I could use it without my fingers taking up real estate. But the real beauty of it is, if I ever want to change it up I can get a new phone, pop the SD card out put it in any other Android 2.1 phone and enjoy all the great new hardware feature my previous phone didn't have. Going with Android means you have the choice of whatever phone you will have over the years.
And Irock honestly, I think Apple is pretty much the antagonist of Capitalism.