My $.02.

I bought a Lumia 928 about a year ago because I really (really really) like the WP8 metro UI.  Really slick, customizable, and interesting.  I was using a Galaxy Nexus android.

Moving over was easy.  I physically took my SIM from the GN and dropped it into the 928.  Done...  Since all my contacts were setup in Google - they pretty much came right down once I created the Google account on the Windows phone.  There is also an app (Transfer My Data) that you can put on your WP to transfer existing SMS & Pictures via bluetooth (I think it can do music now as well).  From there it was just a matter of installing the apps I wanted.

There is a store on the phone & on the web just like google play or the apple store - slightly different UI (of course), but basically a collection of apps you can install.

If I had to do it over again, I would probably run the Lumia on WiFi for a few days (continuing to use my old phone) and get it all setup before moving the SIM.  This way you can take your time with it - you're not stuck on an all-day process trying to get all your apps in order (or trying to find replacements for the ones not available on WP platform). 

There's the rub - what actually kills me personally is the lack of Google Voice/Hangouts & Verizon Messages.  I could get by without all the other Google stuff I used while on Android (books, music), but I use Hangouts a lot for work, and Messages (over WiFi) saves me a fortune when I travel (no more $.50 texts overseas).  I've been bouncing back and forth between the two phones for now - I pretty much am sick of android, but cannot fully commit to WP either.

I signed up for the Preview for Developers from MS, so I'm on the current release of 8.1 (with Cortana).  Pretty significant improvement from 8.