Lumia questions - potential buyer

So my girlfriend soon needs a new phone. She's currently on a WP from LG and generally likes the platform. For and foremost the Lumia 920 comes to mind as her next device - here are some questions:

I heard multiple times from different people that the Lumia often times randomly hangs up or restarts itself. Can you confirm that? Is this a problem of the Nokia hardware or a general problem of WP8? What other problems are there with the 920? Would you recommend it?