I think a very important thing to consider about the "functionality" of the phone lies in the economics driving it's development. IF you are dependent on core features and functions, switching phones requires you perform your own due diligence in what features you can and can't live without. A flip phone will make basic calls flawlessly. 10 years ago everyone had one and Blackberry became king with mobile plans and email clients because that's what people needed. I had an HP PDA with Windows CE, a Blackjack and a Blackberry 8100. All very fun and completely uncapable of surfing the web. If you wanted web surfing and desktop productivity, you bought a laptop... then Apple reinvented how we used phones. Many are quick to forget how limited Apple products were (and still are in many rights) with regards to open functionality. THEY STILL DON'T SUPPORT FLASH!
As people became more mobile, we saw netbooks (trash) and then tablets (why?) and the ultra-books (cool) and then tablets again (sweet) that gradually paved the way for us to truly become mobile power users as technology was able to support the demand we had for the devices functionality.
The core of Microsoft business is in enterprise, Apple has and always will be focused on the end-user, it's what they've invested in for years. Google- it's just google, they are a brilliant team of developers that entered the game with a lot less baggage (legacy systems) that the other two which is what has allowed them to develop in a new market much faster.
I've been researching phones and reviews for two months at an OS level to see what was and was not possible. I had an iPhone 3gs/4/4s and loved it, it was the Honda Civic of phones. Came with a lot of options, easy to use, dependable and hard to mess up. I then got an S3 with was fantastic, lot's of options and cool features. More learning curve for more fun, however- the security vulnerabilities in the market place and constant maintenance of apps was a bit of a chore when every app purchase requires looking into the developer to ensure the permissions were kosher.
I've had my Icon for one day no, the power cycling thing is a little bit of a put out (If it's plugged in and charging and I shut it down, it just reboots). However, being able to edit functions in excel is amazing, all of the general apps (Pandora, Spotify, Netflix, Mobile Banking Apps, LinkedIn, Fandango, StubHub) are there. There are permissions that Windows OS has to fight for with Google, and Apple because they all three are competing for a market and tried to build sustenance for their own ecosystem. So far, I love the phone. Lot's more research into functionality and configuring it to do what I want, but that's technology. I have a laptop (Windows 7), two tablets (Android and Windows 8.1), and a desktop. I know what I have to do where and have been around long enough to know that snake oil doesn't cure everything. I'd personally like to see the Windows phone pull through which is why I invested my dollar there. I don't trust all of my personal information with a company that wants to make "all information available to anyone" and has their heart in advertising. Apple doesn't have the clout to pull enterprise level business, and is unfortunately lost without Jobs (5c... a cheaper phone for the masses? How'd that work for the Mercedes C-Class?) Microsoft will not spend money in a market that does not show promise, people forget the meaning of a dolar and IOU. Invest and seek return or spend and seek demise.