I was in the same boat you were and decided to jump ship onto the WP platform. Before that I had been on android since 2008 until this year, then briefly on iOS for a month before switching in May. What drew me to WP was the amazing camera and I have not been disappointed. I have really enjoyed the responsiveness of the OS and have no complaints as it responds quickly and swiftly as it should. I found myself using the live tiles a lot in the beginning and customizing my homescreen during the first month of use. The battery life is what is expected and gets me through a 12 hour day, sometimes longer.
However, what has disappointed me is the lack of apps. As many have stated here the majority of the most popular apps are available, though the features on these apps many times lack the features of their iOS and Android counterparts. They are essentially barebone apps seemingly having been released to appease the WP crowd. Many of these apps are not frequently updated if they've ever been updated at all. When they are updated there's no guarantee that they'll have the features of iOS and Android. One example of this is the eBay app. So although there are many popular apps available, keep this in mind before switching over.
Another disappointment is the lack of Google support. There are many alternate apps available that function just fine such as those that work similar to YouTube and Google Drive. MetroTube, the youtube equivalent app, is very nice made and goes to show what can be done when a developer puts in hard work. The GMaps, google maps equivalent, functions fine but is not fully featured like the real google maps. It is not polished and the speed leaves something to be desired. I use it over the Nokia Here Maps to find places and there is an option for navigation that will open up Here Maps to give you navigation, since the app itself does not offer navigation. If you use hangouts to chat, then there is only one option called IM+. This is as barebones as an app gets and it does a sub par job. I experience frequent disconnections and notifications of new IMs are not reliable.
All this brings me to another gripe which is email. Gmail and yahoo mail is what I use the most. I thought the android and iOS apps were great but there is none of that to be found here. Since there is no google support there are only a few options to choose from. I found MetroMail to be the best but far from good. The main reason is that it doesn't support push email. So if you're expecting to get emails instantly you will not because it's not supported. Metromail says it supports it but I have not found that to be the case. With yahoo it's the same thing. The best you can do with any non-Microsoft email is to add it to the native email client included in WP. It will still not give you push email and is limited to fetching emails every 15 minutes. It does what any email client would do, but not fully featured like gmail or yahoo so don't expect that. So unless you have a microsoft email account you'll experience a subpar email experience.
Browsing experience is also something that is lacking. I used IE for all of one day before I switched over to a third party app. There is no back or forward button on IE. If you're browsing and press the back button on the phone, it will indeed take you back to the previous page. However if you're browsing and switch to a different app and then back to IE, then that's where the lack of the back button is sorely missed. Pressing the back button once you're back in IE will take you back to the previous app or homescreen, wherever you previously were. The only way to find your previous page is to go into the history and find it there. This to me was and still is flabbergasting. There is no tab support either though it offers almost everything else. I ended up using UC browswer which I found to be a smoother and overall better experience. It supports tabs and has a back and forward button. It does have its glitches but I didn't find a better option.
I was going to head into the Maps experience of WP but decided I'll put an end to this right now, though I could write about that if you so wish.
Overall I would say WP is a decent OS. Like I mentioned the hardware, camera is great. No iphone or android can come close to it now, though they are catching up. The build quality of the Icon is solid, great screen, and decent battery. The OS is quick to respond and is reliable. Cyan will add features that look tempting but I have all but had it with the lack of the quality of apps, poor non-ms email support, an okay browsing experience, and and okay map/navigation system. To me there are more negatives than positives and therefore I will be leaving WP.
I hope this sheds some light and helps in your decision. I only wanted to share my experience and presented things as fair as I could. Good luck with your decision.
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