I can only go off my experience with my partners Lumia 800 that she had... worst OS on a phone I've ever used, honestly the phone would have been better with Symbian on it.
Firstly the customisation that you've come to know and love from Android, forget about it cos there isn't any... at first those snazzy little tiles look great but then the whole thing gets boring quickly and people remark how slick it runs but there is hardly any detail in the UI, all black backgrounds with white text.
The app store is threadbare and what it does have is overpriced.
No bluetooth, you can't even share files with a phone that is the same.
Settings like MMS can be made very difficult to get and work due to Microsoft not allowing push messages from certain carriers, even T-Mobile didn't know how to get it working on my wifes Lumia.
While this might not be a concern to anyone getting a windows 8 phone, anyone who had just got a Lumia on a two year contract will tell you that Microsoft wont think twice about stopping updates for older phones (two weeks old in our case) which for me was unforgivable, Nokia then slashed the price in half which meant I got