Let's not kid ourselves, here. Android is a very good mobile OS, and has some great features that set it apart from other platforms. Google continues to innovate and will likely bring some interesting updates in its next version of Android (Key Lime Pie). The way Android goes about things appeals to many people. It is definitely the most customizable mobile OS out there, and yes, that can lead to bloat and clutter. I think if you're going to give Android a fair shot, you need to try a Nexus device to get the "pure" Android experience without all the extra carrier/OEM bloatware and UI layers.
That being said, I have decided I'm done with Android. My reasons for leaving are many, but the main reason is that Google's products and services are all geared towards harvesting data and information from individuals to serve up targeted ads to them. Many have no problem with this, but I just didn't feel comfortable owning one of their data collection devices (Galaxy Nexus) any longer. Besides, I prefer Microsoft services (Outlook.com, SkyDrive, Skype) over Google's, so it made sense for me to give Windows Phone a shot.
Overall, I've been impressed with my Lumia 521 in the week I've owned it. The Start Screen is a great combination of the tired old icon layout of iOS and the widget capabilities of Android into a sleek, tiled interface.
I am, however, a bit concerned about Microsoft's commitment to the Windows Phone platform. Their latest move of rolling out Skype video messaging to just about every platform EXCEPT Windows Phone has me scratching my head wondering what in the world they were thinking. Shouldn't they have done the exact opposite? How embarrassing.
Anyway, I'll be using this 521 for another 2-3 months before I make my final verdict and get a high-end smartphone.