I've used Lumia now for about week. Not as my main phone as I don't have a Sim for it yet. But as a quick verdict: it's nice. Vet smooth. But it's boring. Compared to harmattan, which is exciting to use, it's just boring. Some of the apps are very nice and the metro interface has good things in it.

I will try using it as my main phone for few weeks, maybe I can give a more refined opinion then.